Vista - Vista doesn't shut completely down. Out of ideas

So I have been testing Vista Ultimate 32bit SP1 for a week now to see if Vista is ready for primetime. I almost ironed out all bugs that was holding me back from switching from winxp.
All except one.

I can't make Vista shut down completely. It seems to turn off, but all fans keep spinning. No matter how long I wait.

I'm not a novice computer user so please don't tell me I might have mistaken sleep, hibernate with SHUT DOWN

Hope some of you experts can help me.

Thanx in advance

- NightRhyme

System specs:
CPU: E6850 3.42Ghz
Mobo: Asus p5k Premium black pearl
Memory: 4 x 1gb Crucial DDR2 BallistiX PC8500, 1142mhz
HD: WD Caviar Blue 750gb
PSU: Corsair HX520W
GFX: Club3D HD 4870, Cat 8.8

Are you clicking the yellow button on the start menu? If you are then that's the sleep button. I know you said you're not mixing sleep with shutdown up, but I made the same mistake the first time I was using Vista.

No I am not.
Of course I am not.

I even went so far as to disable SLEEP and HIBERNATION completely to make absolutely sure there was NO mistake.

I have been working on this specific problem for 2 days. And I am sorry to say I now know everything there is to know about sleep, hibernation and SHUT DOWN.

I found some guys with the same problem.
The solutions mentioned however doesn't help
VISTA ShutDown Problem - Tech Support Forums - TechIMO.com

No one has any suggestions ?

I'm going slightly mad here

Odd as at may sound, I have found that some USB devices have caused my system to improperly shut down, or restart rather than shut down. I think they continue to "chat" with the system, or something. In my case, it was a gaming mouse. Just try removing each device, and see if one of them being removed causes the system to act properly, again.

You could also boot to safe mode, and without anything in memory such as antivirus and firewalls, see if it will shut down correctly. Bad disk sectors are also a problem, so why not check your disk for bad sectors, and the like?

Just a guesses, of course...

If it still wouldn't work after all check mentioned above. Check for bad SATA cable and bad SATA contacts. I tell everyone to check this because it happens allllll the time and it make my work and play miserable! Just go unplug and plug the cable back onto the HDDs and MB to see if it helps. Good luck!