Given it's XP it could be that old and slow. But here we have little to work with and then words about fans. Fan speed on newer PCs speed up when needed which can really upset some owners. Also, fans can age and do odd things. At about 5 years many fans need replacement. And then we have owners that didn't know.
Bob
Hi Forum.
About a year ago I upgrade ram from 1 to 2 gb and updated Bios. Since then the computer is running slow and the cooling fan races erratically. Playing video from files is ok, but not perfect. I can hear the fan pitch change. Same thing with youtube, ok, but not perfect. Embedded videos in websites that aren't connected to youtube are terrible, as is Hulu. I have a fresh Win-XP-sp3 install with all needed drivers and no improvement. I dont know if I got defective ram cards, or maybe it's the wrong bios(it was the only one at the intel or emachine websites). I would like to re-use the bios # that originally came with the PC, but don't know how. I saved the number, but don't know how to use it. I don't even know how to word the question for google. Is it the bios serial # that I saved? What else would make the PC fan race and slow everything down?
Thanks anyone.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic