You have probably got some spyware installed, search this forum for spyware removal, you may also have some heavy load background proccess running such as a dc client, or kazaa etc? or even norton ghost or the likes, if you do a cad (ctrl alt del) and look in the proccesses section you will see what is eating up your cpu

Yeah you probably have 1 of 3 things or all three or a combo of 2 of 3 (you get the idea)

1) Spyware
2) Virus
3) Too many darn programs running

Solution?

1) Reformat (nah...not the best option)
2) Scan for virus's/spyware (use adware..download.com has it)
3) Have less programs running in your startup...

(another thing you could do is check your bios, maybe somethings goofed up in there...who knows!!!)

---------
Webpage