Shut down in Vista

I'm not being an ass by telling you this, but I have been testing Vista and it's more trouble than it's worth. Blow Vista away and replace it with XP SP2.

Trust me, you will sleep better and have less problems.

Could be bad memory, or a hardware issue. See
http://www.computing.net/windowsvista/wwwboard/forum/595.html
And http://forums.nvidia.com/lofiversion/index.php?t26871.html

And check power options.

Mine works ok, and I use TweakVI which can put some reboot, shutdown, etc, shortcut options to the desktop.

I'll pray you get it fixed.

Reinstall your vista, I have never had that problem, don't use software that was hacked.
i use both 32 and 64 bit and I'm happy