Power-Supply Problems
The most easily recognized problem is a complete failure of the power supply. This is easy to detect because in the event of a failure, the computer will not begin to boot up (no lights, no sound). If there is apparently no power, be sure to check the power source and the plug at both ends: the outlet and the computer.
If you are experiencing intermittent failures such as memory loss, memory corruption, or unexplained system crashes, don't rule out the power supply. It is often the culprit. Fortunately, it is easy to check and replace.
Good power supplies have line-conditioning circuits, but these might not be sufficient enough in locations where the power source has substantial quality flaws. If you have problems with several systems, or if a second power supply still does not fix a related complaint, add a UPS with good line-conditioning features.