I negligently went 3 years without removing the dust inside my computer. About 18 months ago, an unknown computer hardware malfunction caused my Windows XP session to be interrupted by a momentary loss of electrical power (a "flicker"). The screen went blank and then the computer started to reboot. Over time, I noticed that this flicker occurred if the computer had been on too long. The max session time before the flicker would occur has been steadily decreasing, from 3.5 hours to 2.3 hours to 1.7 hours. When the computer was on but inactive, the internal temperature hovered at 53 degrees Celsius. Recently, I removed the dust inside my computer, and the (inactive) internal temperature began hovering at 50 degrees. Subsequently, the computer flickered after 1.4 hours, and the next day the computer would not turn on at all. When I attempt a cold boot, I apparently get no electrical connection and no hard disk activity lights. What is the most likely cause? a) power supply failure b) motherboard failure c) CPU failure d) other Hardware is a self-built 7-8 year old 3GHz P-4, with a PSU probably around 500-600 watts (as best as I can remember; actual specs are unavailable). Assuming that I remove the PSU, is there a way of independently testing it with household appliances? Alternatively, is there a cheap way of testing it at a computer hardware retail store (e.g. Fry Electronics)? If the PSU has failed, is it advisable to try paying for its repair? Alternatively, will a new PSU necessarily be compatible with my old hardware?