1.  Your computer may contain a virus.....
Perform a free virus scan:  
http://security.symantec.com/ssc/home.asp?j=1&langid=us&venid=sym&plfid=23&pkj=FHGUCVGZBZTVOGXFSTZ
2.  Your computer may contain some spyware.....
Download Ad-Aware and run it:  
http://www.lavasoftusa.com/support/download/
3.  Your system may have incorrect or unsigned drivers.....
Go to Start > Run and type:  SIGVERIF  , and hit enter.
HOW TO: Verify Unsigned Device Drivers in Windows XP
http://support.microsoft.com/default.aspx?scid=kb;en-us;308514
You may wish to perform a "tune-up" that may help:
1.    Perform a DISK CLEANUP:
(Start > Programs > Accessories > System Tools > Disk Cleanup)
2.    Go to Start > Run and type:  CMD  , and hit enter.  In the Command
Prompt window type:  CHKDSK /F  , and hit enter, answer "yes" and
reboot your computer.
3.    Afterward, perform a DEFRAG of your hard drive.
-- 
Nicholas
----------------------------------------------------------------------
| I am running XP and the "System Idle Process" is hogging 
| the CPU slowing everything to a standstill.  What can I 
| do?