PC starting to act really wierd lately, while just idling with only msn, irc and winamp running my CPU jumps up to 25-80% of its capacity, just mad laggy. I've scanned with AVG and found no virus what so ever, could it be that i havent defragmated my hard drive in a long time?

Really annoying, and i dont want to reinstall windows over it. Grateful for any help on this matter. I run with Windows XP btw and these are my PC specs:

(08:34:33) (pinball-) (CPU2) Intel® Pentium® 4 CPU 3.00GHz @ 3010MHz (ASUSTeK Computer INC. P5PL2 mainboard) (RAM) 1GB, 642.64MB free (HDDs) 323GB, 21.1GB free
(08:34:33) (pinball-) (VGA1) NVIDIA GeForce 7600 GT (256MB), 1024x768x32, 85Hz (OS) Microsoft Windows XP Home Edition (SP2), 17m 14s uptime, 1d 14h 18m 30s uptime record

PIC: http://i6.photobucket.com/albums/y210/Pinnitaj/buggjdfdsf.jpg