I've recently started having problem with my PC turning off on me. Once it turns off, there's this beeping sound from the BIOS and it will not let me power up again. If I do turn it on and leave it on, the beeping eventually stops and the CPU cooling fan ramps up in speed and will remain that way until I press the power button on the front of the tower (in this situation, I never make it to the Windows environment). If I leave it long enough, it powers up again fine and goes into Windows, but if I leave it on for too long, it does the same thing again. It looks like my CPU is overheating, but my cooling fan is working fine (I can see and hear it running). Should I upgrade with a higher speed cooling fan? Maybe replace the hard drive? I've open up the PC tower and clean heat sink, cooling fans (both power supply and CPU cooling fan) and it does run fine after I do that, but not for long. I can see the computer getting slower and slower after I've been running it for quite some time. If I try to play a game which requires a lot of processing memory, it simply accelerates this process. The computer is only 3 years old. I am not sure what to replace? I'd hate to spend money on the wrong component. Any advice would be really appreciated. Thanks.

You claim the CPU is overheating but you didn't say what the temperature reading is. When a P4 reaching a certain temp, it automatically underclocks to a lower speed...it's called "throttling". That *might* be what's happening but without knowing the temp, it's just a guess. Also, the beeping should have some sort of pattern. "If my answers frighten you then you should cease asking scary questions" - Jules Winnfield (Samuel L. Jackson) in Pulp Fiction