Dear DAL,
Since a few days, my computer doesn't want to shut down. The command instead reboots it. Same thing for the "Hybernate" command.
I have done a system restore to an earlier point but it didn't work.

Let me know if you have a solution for me.
Best Regards,
Carine

First you need to change the "Automatically Restart" option on a System
Failure. System Properties, Advanced, Startup & Recovery. Uncheck
the option box "Automatically restart"

Are you getting a Blue Screen of Death before your reboot, My suggestion above is for Vista Rebooting on system failure, If you disable Auto restart, and you are experiencing a BSOD, It will probably hang at the BSOD.

This will allow Vista to show the
register contents when the BSOD is triggered. On the next BSOD jot
down the displayed information. It will give you a better indication of
what caused the exception. Post the details here.

Abrupt power offs aren't good either. Can leave the disk in an inconsistent
state (Dirty). To verify the system volume's condition, Open a CMD prompt
box and type:
FSUtil Dirty Query C:
if the FSUtil returns "Volume - C:: is NOT Dirty, then the drive itself is
OK.

I don't run Windows. I pulled this info off the web. If You wan't to read up on it, Here is the link.Vista Won't Shutdown - Vista Help

Hello rokytnji and thank you for your post.
I am not very geeky so I don't know where to find the system properties.
Also, when the computer tries to shut down I don't get the BSOD. It follows the procedure until the end but restarts from a black screen.

I appreciate your help,
thank you

If it is automatically restarting upon a blue screen, you won't see the blue screen so start by seeing this: Disable the Automatic Restart on System Failure in Windows Vista. Note that you can also right click on "computer" from either the desktop or the start menu, select properties, & then skip to step 4. While you are at it in the same menu make sure Write an event to the system log is CHECKED and that write debugging informations is set for Kernel memory dump from the drop down.

But I don't have a blue screen when it's shutting down.
BTW, I checked what you said and everything is fine...

How far does it get in the shutdown process?

until the end, the screen is pitch black, but instead of the power shutting down, the power button stays on and the computer reboots.

Not being a Windows expert. I was just wondering, Have you made any changes in bios before this reboot problem surfaced?

Hi,
No I haven't touched the BIOS (won't dare to)

Well, if you didn't touch the bios (I was just trying to rule out things that could cause this problem) then it is definitely a Windows Vista problem, Could be driver related or whatever. Being a full time Linux user, I won't be of much help. You need a Windows user to help find where your problem could be. Sorry I can't be of more help to you.