I have had a similar problem, when running avast it would get to the windows dir and reboot, and since the Internet Explorer had been reset from ver 7 back to ver 6, I had uninstalled IE 6 and tried to install IE 7 but everytime I deleted IE 6 and before I could re-install IE 6, It would reappear - these files would come back
[iexplore.exe, iedw.exe, hmmapi.dll, and the Connection Wizard dir].
When I try to upgrade IE 6 to IE 7, Microsoft does a virus scan and when it gets to the Windows\System 32 dir
the system reboots.
I do not Know what Malware is causing this problem and I can not seem to get rid of it.