98% CPU usage -- unless I open Task Manager

OK, I'm stumped and a bit scared. My computer (about 1 yr old, HP, notebook, running Vista SP1, 2 GHz dual processor, 2G system RAM, Internet Explorer for browsing) runs REALLY slowly....unless Task Manager is open.

 

When I open Task Manager, it shows about 98-99% CPU usage.....which immediately drops down to about 6-12%.

 

I have Task Manager set to sort by CPU usage, but the culprit never appears. Top hog is always iexplore.exe when it's running, which varies from 5% to 50% if a new page is loading.

I've virus scanned, to no avail.

Any ideas? Sounds like a virus to me, and a devious, hidey one at that.

Happens all the time, whether restarting, starting up or waking from sleep mode.

Happens even with no apps running.

Disk space is not maxed out.

Our stopgap measure is to constantly have Task Manager open. This solves everything.

 

Anyone heard of this? Also, there are other reports of people's CPU maxing out -- perhaps they can check the Task Manager thing out, too.

Thanks for any assistance.