Have you checked msconfig? How many startup items are running? If your not using ipod service, you don't need it running so you should disable everything since you don't have antivirus.
that trend micro house call is found at www.pc-cillin.com I use it all the time
Also of course if you don't already have em get Adaware, and Spybot: Search & Destroy, use both of them plus the www.pc-cillin.com to get all the pr0n residue off your computer Just messin with ya there
Virii or spyware is the only thing that I can think of as been said by a couple people already that would cause a jump like that.
If you don't have that Ipod thing then get rid of itl.
Also go to www.download.com and search for 'Startup Control Panel' and install that program.
Then go to Start>Control Panel> Startup and delete anything that you know doesnt belong there.