|pigsyj, a couple of things come to mind. Might be either/neither. First thing is a trojan/worm. Be aware that a virus and a Trojan are similar, but not the same. Many times, an AV detects one it can't clean, other times, it gets missed entirely.|
If you need to clean one, Superantispyware can do the job and you can get it free @:
among other places. They have a Vista compatible version if needed.
If it turns out that you need to use it, be sure to update prior to running and disable 'restore' (restart after cleaning) so it doesn't get put back. They just released a new update recently and it changes all the time. Things are in a constant state of flux.
The restore thing is critical. May not be your deal at all, but won't hurt anything to try.
Second FWIW, Windows seems to have been plagued with shutdown problems of one sort or another since day 1. I use a standalone shutdown proggie (for convenience) called 'Slawdog' (said to work on all versions). Get it free @:
among other places. Works good and I drag/dropped the icon into my quicklaunch so it'd be handy for use.
May not help, but won't hurt.
Ed in Texas.