Certain types of hardware errors will prevent your computer from working at all, even if it appears to be powering on properly. A faulty power supply or hardware that isn't properly fitted into its slot may let your computer turn on, but will not let you access the BIOS or any other systems. Resetting your CMOS can help fix any BIOS-related issues and let you troubleshoot which settings caused the issue, and this reset can be performed even if you can't see anything on your screen.
Check that your monitor is working by plugging it into another computer or by plugging a different monitor into your computer. In case there is any issue with your graphics card, plug your monitor into another graphics port to see if anything appears on the screen. You may only have this option if you have a graphics card separate from your motherboard's integrated graphics card; your monitor may turn on when plugged into one, but not the other.
Open your computer's casing, then remove and reseat your hardware, such as your RAM, graphics card, wireless card and anything else you are able. Sometimes your hardware may become unseated even if your computer hasn't been moved; this is a process called "chip creep." Reseating your hardware makes sure every piece is secure in its slot and that your computer can read it correctly.
Test your power supply by plugging your computer directly into a wall socket instead of a surge protector. This will help verify that your computer is getting the right amount of power. Also verify that your power supply's voltage switch is set to the correct amount. If the fans are running very slowly or very quickly immediately upon startup, or if fans are failing to spin at all, your power supply may be broken and in need of replacement.
Remove the small, circular battery from your computer's motherboard, then replace it. Removing the battery resets your computer's BIOS settings and may correct some issues. If this corrects the problem you can change your BIOS settings back to what they were previously, but make and save changes one at a time to help you figure out which setting caused an issue.
You may not be able to remove the battery on certain models of motherboards. If you cannot, you will need to look up specific instructions for the model you have.
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