Symptom: Computer won't boot up
Could be: A software issue.
The fix: Sometimes the inability to boot up and get into the operating system indicates a corrupt system file, says Bob MacDonald, vice president of technology services for Staples' EasyTech service. Some off-the-shelf diagnostic tools will scan and, if possible, repair the problem.
The alternative, though, might be to reinstall the operating system -- a time-consuming task that could mean data loss, particularly if you're not backing up regularly, he says. More advanced diagnostics and repairs are best left to IT professionals, who can usually protect against data loss.
Symptom: Computer won't boot up past POST ("power-on self-test," the preboot sequence)
Could be: A hardware issue.
The fix: Take note of any messages or beep codes -- even if they seem cryptic -- because they give details of the problem, Obenshain says. You can use them to search online or to search a vendor's Web site for information about what might be wrong and how to fix it.
In addition, try to isolate the problem by disconnecting any external pieces of hardware connected to the machine and rebooting to see if any of them could be the problem, Obenshain says.
If you added a new piece of hardware and couldn't boot up, it could mean that there's something physically wrong with it, or that there's some incompatibility between it and your computer, or that the driver on that device isn't compatible with a piece of software on your machine, he explains. "So the quickest, simplest test is to take off the new addition and see if that's the fix," Obenshain suggests.
After a few weeks without additional problems, you'll have a better idea of whether you addressed the real problem, he notes.
Also, those who are more tech-savvy can open up the desktop casing to make sure all the cables are secure. Sometimes a cable can be jostled loose when a computer is moved.