If the PC does not start or Windows annoys with regular bluescreens, good advice is expensive. We’ll show you how to troubleshoot typical computer problems on your own – and how to solve them.
Many users have already had experiences with a computer that no longer starts or that regularly says goodbye with a blue screen. The causes for this can be manifold: A completely dusty system or a loose connection cable can be the triggers as well as defective hardware, a damaged bootloader or too high overclocking.
Table of contents
In this article, we’ll take a closer look at the most common sources of errors and show you how you can get to the bottom of the startup problem or the cause of the crash. We cover all common scenarios: The PC won’t turn on at all, the computer starts but doesn’t load the installed operating system, and Windows crashes regularly.
The most important information first: If your computer no longer starts or Windows crashes every few minutes, it’s important to keep a cool head and systematically tackle troubleshooting. Systematically means in this context to always change only one parameter. If you suspect that a defective RAM bar is responsible for the problem, it doesn’t help to change the BIOS/UEFI settings in the same step, because you don’t know afterwards which change led to success.
Here you can quickly jump to the individual problems:
1. PC does not turn on at all
1.1 Check the power supply
1.2 Check power button and reset button on computer case
1.3 Inspect voltage supply on mainboard
1.4 Take a closer look at the power supply
2. PC starts, but does not boot
2.1.1 Reset the mainboard to default settings
2.1.2 Replace CMOS battery
2.2 Processor gets too hot
2.3 The RAM can also stop the PC from starting up
2.4 Check the graphics card
2.5 Watch out when buying a mainboard
3. PC starts, but brings error messages
3.1 No boot drive is found during computer startup
3.2 Bootloader repair and hard disk data recovery
4. PC starts, but the monitor shows no picture
4.1 Basic check
4.2 Check inputs one after the other
4.3 Replace graphics card
5. Windows starts, but crashes again and again
5.1 Permanent crashes under load
5.2 Computer crashes when connecting a device
5.3 Sporadic crashes
5.4 Find causes of crash with Windows on-board tools
5.5 Perform a targeted bluescreen analysis with a freeware tool
5.6 Bluescreen analysis for professionals: Windows Debugger
1. PC can’t be switched on at all
If the PC doesn’t make a sound at all after switching on, the fans don’t start spinning and the RGB lighting stays off, there is usually a problem with the power supply. The range of possible causes goes from a loosened cable to a broken power switch to a defective power supply unit.
1.1 Check power supply
The first thing to do is check the basic power supply: Is the cold-device plug, which is plugged into the back of the PC, also firmly seated?? Make sure the other end of the cable is plugged into a power outlet? Is a possibly used multiple socket switched on? If the main switch, which many power supplies have, is in the on position, the main switch is in the off position? To really rule out all potential sources of problems, it also can’t hurt to plug in another device to the outlet the computer is plugged into to see if it is working at all.
1.2 Checking the power button and reset button on the computer case
To find out if the power button and/or the reset button are causing problems, you need to take a look at the motherboard. For this, you first have to remove the side panel of the case to get a clear view of the motherboard. Identify the thin cables leading from the power button and the reset button to the motherboard and check if the tiny, two-pin plugs are firmly attached to the respective pins – see picture below. By the way, on modern motherboards the connectors are labeled, which makes identification easier. Otherwise you have to look up the pin assignment in the manual of the mainboard.
Disconnect the reset plug and press the power button. If the computer now starts, the problem is clearly related to the reset button. Otherwise, also disconnect the plug that leads to the power button and short-circuit the two pins by holding a paper clip or screwdriver to the two contacts to bridge the gap. If the PC starts, you have identified the problem: either a cable break or a defective power button. If you don’t want to buy a new case, connect the plug that leads to the reset button to the power button connector and use the reset button to turn the computer on and off in the future.
Notice: Not all cases have a reset button.
1.3 Inspect the power supply on the mainboard
If the computer still doesn’t turn on, the next step is to check the connection between the power supply and the mainboard. Unplug the wide 24-pin connector and the four- or eight-pin 12-volt connector(s) and see if the components look scorched or melted. If this is the case, your PC has obviously fallen victim to a power surge. Whether this was caused by a lightning strike or a defect in the power supply is irrelevant. More importantly, such an overvoltage can damage all system components in extreme cases. In such a situation, you can’t avoid buying a new device.
1.4 Take a closer look at the power supply
If, on the other hand, the connections and motherboard look undamaged, there’s basically only one source of error left: the power supply. One piece of information beforehand: That the power supply gives up the ghost happens much more often than you think. Mostly the defect has thermal reasons. Dusty fans may be preventing components from being properly cooled, resulting in permanent overheating. But also the electrolytic capacitors used in power supplies, known as electrolytic capacitors for short, are potential causes, since these components only have a limited lifetime. If your PC suddenly switches off, this is also a sign that something is wrong with the power supply.
The only way to find out if the power supply is defective is by using a replacement device. Only users who own the appropriate equipment and have the necessary knowledge can measure how the output voltage is.
Don’t forget: For safety reasons, do not unscrew the power supply under any circumstances. A repair is out of the question anyway for cost reasons – good standard ATX power supplies with 400 watts are already available for under 40 euros, for example be quiet! System Power 9 .
When buying a power supply, you should never go for a "China firecracker" but use a branded power supply with the necessary protection circuits. Many PSUs also have 80-PLUS certifications, which attest to a higher level of efficiency. Recommended power supply manufacturers are be quiet! , Corsair or Seasonic . The good news: Dismantling a power supply isn’t even a challenge for users who aren’t that skilled in their craft. Because basically, all you have to do is unscrew four screws and unplug a few connectors from the hardware. It’s best to remember which cables were plugged in where, or make a note of it so that you don’t forget any cables later.
When looking for a replacement power supply, you only need to know what power the component is supposed to deliver and which connections you need. If you are not sure, just put the removed PSU in a bag and take it to the store so the salesperson knows what your PC needs. If you prefer online shopping, take a look at the sticker on the power supply to find out the wattage and the form factor, usually ATX. Alternatively, you can just google the model name.
Removing the defective power supply and installing the replacement power supply is usually done in less than ten minutes. Insert the component in the designated place and screw the power supply unit to the case. Then connect the necessary plugs. Normally, this is the already mentioned 24-pin connector and one or two four- or eight-pin 12-volt connectors. If your graphics card requires an additional power supply, connect this cable as well. Also, do not forget to connect the hard disks, SSDs or drives to the power supply unit. Double-check all cable connections, plug in the IEC connector to the power supply and set the component’s main power switch to On. After pressing the power button, the computer should start up again.
Hint: Older motherboards often have a 20-pin connector. This is not a problem, since the 24-pin connectors are designed to be used with the old connectors as well.
2. PC turns on, but does not boot
The computer turns on, but instead of continuing the boot process as usual, the device emits loud beeps or displays an error code on the mainboard’s status LEDs. The BIOS (Basic Input/Output System), or the much more modern UEFI (Unified Extensible Firmware Interface), is responsible for this. It carries out a quick check of the most important components during startup and sounds an alarm in case of problems. This can be done either visually or acoustically.
If a beeper is installed on the mainboard, the BIOS/UEFI reports with certain tone sequences: Depending on how often a beeper repeats or how long the tone lasts in which order, the error will be explained. In the tables below we have listed the beeps as well as potential causes and possible fixes for Award/Phoenix and AMI-BIOS. Information about the components of other manufacturers, such as Intel and AMD, can be found in the mainboard manual and on the respective support pages. If you use a pre-configured computer, for example from Acer, Dell or HP, you can find this information on the manufacturer’s websites.
Many mainboards have so-called diagnostic LEDs installed in place of the beeper, which provide direct information about whether the processor, the graphics card or the mass memory is causing the problem. On higher quality motherboards there is also the possibility that the BIOS/UEFI displays two-digit codes via a small segment display or a display on the motherboard – just look up the meaning of these codes in the manual of your motherboard.
Regardless of which way your motherboard uses for error output, the source of the error can be limited to the RAM, the processor, the graphics card, the system memory or the motherboard itself.
How to proceed once you have located the problem can be found in the following sections: Mainboard, Processor, Memory, Graphics Card and System Memory
2.1.1 Reset the mainboard to default settings
If the error message indicates an error caused by the BIOS/UEFI itself, you should reset the mainboard to factory defaults. If the screen is still on and the PC starts booting, then press a specific key immediately after powering up. Which button you have to press depends on the BIOS/UEFI manufacturer. A look at the screen messages displayed after switching on the computer or in the mainboard manual provides information. Normally one of the buttons works F2 , Del or Esc . Then in the configuration screen look for a function to reset – see picture. This deletes all user-defined settings.
If you can’t get into the BIOS/UEFI configuration screen at all, there’s no other way than to reset the component the hard way – via CMOS reset. CMOS is the abbreviation for "Complementary Metal-Oxide Semiconductor" and refers to a volatile memory chip in which the BIOS/UEFI saves its parameters. This chip loses its settings as soon as you remove the button battery and thus disconnect the power supply.
Proceed as follows: First of all, disconnect the PC completely from the power supply. Then ground yourself at a radiator and remove the side panel of the case. Locate the small button cell on the mainboard – see picture. You may have to remove a component like the graphics card for this because it covers the battery. The button cell is held in the socket with a latching mechanism. To remove it, you need to push the small lever to the side and disconnect the battery. A small slotted screwdriver can be very helpful, avoid using sharp objects like a knife. Wait about ten minutes until you reinsert the coin cell so that there is no residual voltage, only then will the CMOS device reset itself.
Note With some high-quality motherboards you don’t have to remove the button cell at all to perform a CMOS reset, because the manufacturer has a Clear CMOS button has installed internally or externally. The picture above shows how such a button can look like:
2.1.2 Replace CMOS battery
As already mentioned, the motherboard has a button cell battery so that the BIOS/ UEFI settings are retained even when the computer is switched off. The CMOS battery is always charged during device operation and lasts for many years. However, if the battery is at its end, the PC permanently forgets the time as well as boot and peripheral options. In addition there are error messages at system start like "CMOS Read Error.
In such cases, you should switch off the PC, disconnect it from the power supply, open the housing and locate the button cell. Mostly lithium button cells of the type CR2032 (3 volts, 225-230 mAh) are used. A flat screwdriver is all it takes to get the old battery out. Such batteries, which are also used in watches and car keys among other things, can be found in every supermarket and at gas stations for as little as 1.50 euros.
2.2 Processor gets too hot
If the mainboard’s error message shows that the processor is causing problems, your options for intervention are very limited. Because the CPU can’t easily be taken out of its socket and tested in another system, unless you have several devices at hand. The only option you have is to reset the BIOS/UEFI as described in the previous section. Regardless of this, you should take a look at the processor cooler. If the component is very dusty, you should clean the heat sink immediately.
You can either do this carefully with a vacuum cleaner or with compressed air, the rotor blades of the fan should be held tightly in the process. It’s best to remove the fan or even the entire heat sink. At the same time, you should also check whether the thermal paste has dried up. If this is the case, remove the residue with a kitchen roll. If the heat conductive paste can only be removed very stubbornly, isopropanol alcohol or an alcohol pad can help with cleaning. Then apply a blob of new thermal paste about the size of a pea in the center of the CPU. Spread the heat conductive paste and then mount the heat sink again. Do not forget to connect the fan cable to the mainboard. If you are lucky, the system will restart afterwards, otherwise you will have to replace the CPU.
2.3 Even the RAM can stop the PC from booting
If the error message points to the working memory, you can easily check its functionality. First disconnect the power plug from your PC and ground yourself to a radiator. If your computer only has one RAM module, carefully release the lock, insert the component into another slot so that it audibly clicks into place, and restart the computer. Check all available slots in this way. If the startup behavior does not change, you can still carefully clean the contact surfaces of the RAM with isopropanol alcohol. If that doesn’t help either, take a look at the sticker attached to the latch and purchase a new RAM block with the identical specifications. If the start still fails, the mainboard is broken.
If the motherboard is equipped with two or more RAM blocks, perform this test with each RAM block separately. This procedure is time-consuming, but you will finally find out, which RAM-mirror is defective. If, on the other hand, this check does not lead to the desired success, the motherboard has given up the ghost. Finally, it is very unlikely that all four RAM blocks will break at the same time. In this case, there is no way around buying a new motherboard. The easiest way is to buy the same model again, otherwise you have to make sure that you buy a motherboard with the right socket.
2.4 Check the graphics card
If the mainboard’s error message points to the graphics output device, there are two possibilities. Cheap PCs often don’t have a separate graphics card installed, but the graphics unit is located in the processor. In this case, you should proceed as in the section about replacing the CPU . If your PC has a dedicated GPU, you should first remove it. Before you get in touch with the hardware, don’t forget to ground yourself to a radiator. If the graphics card’s heat sink is dusty, clean it carefully with a vacuum cleaner or compressed air. You can use isopropanol alcohol to clean the GPU’s cotact surfaces. Then reassemble the hardware and don’t forget to reconnect any necessary power cables and the monitor cable to the graphics unit.
If the error still occurs, it is still possible that not the graphics card itself, but either one of the display outputs or the slot of the mainboard is defective. For the former case, be sure to try all the display outputs of the GPU to see if one works. If your mainboard has several PCIe slots x16, you can also test the GPU in these to rule out a defect of the mainboard. If your mainboard doesn’t have another PCIe slot, it makes sense to test the graphics card in another PC. If the GPU still doesn’t work, you’ll probably have to look for a replacement.
2.5 Eyes up when buying a motherboard
If everything points to the motherboard, you have no choice but to replace it. Here you should first answer the important question, whether a new mainboard makes sense at all, or whether you should invest in a new system. This depends primarily on the age of your PC. If your computer is already four, five years old or even more, it might be very difficult to find a suitable mainboard. The motherboard must have the correct socket for your processor and must also support it on the BIOS side. A newer socket is not backwards compatible with older processors, which means that you may also need a new processor. In the worst case, your PC still has DDR3 memory installed, which you also can’t use on a new motherboard with DDR4 slots. In such a case, building a completely new PC often makes more sense.