Brett said:
task manager doesn't show this information.
Task Manager may show the "culprit"; you may just not know what you are
looking at. The item causing your usage may be running as a service or
may be hidden malware. The normal troubleshooting path for this sort of
problem is:
1. Check and see if the Indexing Service is enabled. If it is, disable
it and see if that solves the issue. If it does, case closed.
2. Scan with a current version antivirus (not earlier than 2004) using
updated definitions. Do all scans for malware in Safe Mode.
3. Scan for non-viral malware, starting with free programs like Ad-aware
and Spybot Search & Destroy. Install those programs, update them, and
scan with each program (not simultaneously!) in Safe Mode.
4. After you have ensured that the computer is 100% malware-free, if the
problem persists do clean-boot troubleshooting:
http://support.microsoft.com/default.aspx?kbid=310353
Malke