Hello martian63, welcome to GTG!
This is all to similar to a topic I read through over at
eggheadcafe.com. Granted it deals with the Windows Malicious Software Removal tool, but it's worth a shot. No need to dig through it though, here is the relevant information to resolve the issue:
Just wanted to share my experience with this update that came out on
the 8th of this month that affects the Windows 2000 professional
computers rebooting just before login. After speaking with Microsoft,
it is actually the combination of the kb931768 update, along with a
malicious software removal update for May that came out at the same
time.
If you can boot into the recovery console and do the steps above as
noted by John John to uninstall the 931768 update (mine was named
$ntuninstallkb931768-IE6SP1-2007... (I forgot the rest of the path)),
and reboot after the uninstall, it would still reboot the machine just
before login screen appeared.
However, if you go into recovery console and go to c:\winnt\debug and
look at the log files there, you will see that the malicious software
removal tool actually tagged c:\winnt\system32\sfc.dll as a virus and
deleted the file at the next restart.
To fix this issue, uninstall the update 931768, then type the
following at the recovery console:
expand d:\i386\sfc.dl_ c:\winnt\system32\
After the sfc.dll file is restored, reboot the machine and everything
should come up just fine.
Regards,
Ax