XP Pro Upgrade machine not turning off

We just upgraded a machine to XP Pro from Windows 2000.
Machine won’t shut down and/or restart using the normal shut down button from start menu or even from task manager.
Anyone have any suggestions?

Press the power button on the front of the case and hold it for 4 or 5 seconds until the machine shuts down. Then reboot (you may have to go through the file checking routine when it boots up) and then see if you can shut it down. If not, you may have to re-install windows.