Some reasons that a computer system fails to start include power supply failure, operating system failure and hardware failure. For a desktop computer, a broken power supply results in no response from the computer. For a laptop, a broken or uncharged battery can prevent the computer from starting.
Corrupted or missing operating system files can cause a computer to fail at startup. Certain malicious software can also cause a boot failure by changing system files. When a hard drive failure occurs, files in the drive, including files needed to boot up the computer, become unreadable. A malfunctioning motherboard, which is the brain of the computer, can also cause a boot failure.