Well I know this is an old thread, but my neighbor called me last night needing help. So I went down. Low and behold for about 6 months he has been using that PC with the CPU running 100% the whole time. We tried many of your fixes Efc. None of them got to the root. That is until I looked at the back of his PC again.

Seems he had ADSL connected. But it wasn't a traditional connection through an ethernet port. It was connecting over USB. Well, I unplugged it. Then I checked tast manager for 1 minute no change but after 2-3 minutes the processor went back down to normal levels. The usage dropped. So we plugged back the USB connection from the modem, and bam, it went back up to 100%.

I had a spare 100mbit Linksys NIC. I got it for him, installed it, plugged the ethernet cable directly into the Linksys NIC. Checked taskmanager. and Viola. It works normal now.

I unindexed all the files on his HDD, ran a disk defrag, and put the theme back to windows Classic, to make it run better for him. I think he was happy.

Case closed