Now you know what you can do if your Windows operating system no longer boots. But what if, after switching on the computer, the dreaded bluescreen of death appears or the screen remains completely black? If neither Windows nor the BIOS or UEFI menu have started, there is probably no error with the software, but rather a hardware defect. The graphics card may not be properly connected, there may be dust on the memory contacts, or the newly installed processor may not be compatible with the old motherboard.
To exclude the latter, you should first try to update your BIOS or UEFI. To do this, reinstall your old processor and search for the appropriate update files on the mainboard manufacturer's website. But attention: updating the BIOS or UEFI isn’t without its risks. So be sure to make a backup first.
If the problem still isn't solved, you'll have to resort to the exclusion method: Remove all newly installed and connected hardware (including peripheral devices such as printers and headphones) and restart your computer. If your computer and Windows boot successfully again, start by reconnecting the remote hardware one by one and restarting the computer until you find the culprit. Also check that the cable connections are in perfect condition. It is also a good idea to try out the maybe-defective devices on another computer before disposing of them prematurely.
Sometimes the BIOS or UEFI tones can also help you to identify the source of the error: After switching it on, the computer clearly signals which hardware is causing problems by letting out a sequence of beeps. These tones are different for each BIOS or UEFI provider. For example, American Megatrends (AMI), the US hardware and software manufacturer, has a permanent beep for a defective power supply and a long-short sequence for a critical fault with the motherboard. A single, short tone, on the other hand, always means that the start was successful.