|Some Dell desktops have a known problem, depending on what model you have. But anyway, if you have a Dell desktop with a large heatsink and fan right at the front of your computer then you may have a problem with corroded ceramic capacitors on your mainboard. |
There are a bank of ground plane capacitors that sit right in front of the CPU that go bad. They are easy to replace by anyone with Surface Mount Component soldering skills, but they are not user replaceable. You would have to remove the CPU and test them with a multimeter to be sure, but this is usually the case.
Anything other then that, you could try to reseat your ram and reseat your processor, and try a test power supply.