[RipperRoo]

does windows get as far as the 'it is now safe to turn your computer off' screen?
if so just press and hold the power button on the system case for 5 seconds and the pc will shut down.
you may find this is caused by the acpi funcion being disabled in windows, this is changed through the device manager as seen in the pic, this was taken on a win2k installation but the changes in xp are just cosmetic . be carefull tho, as if the shutdown problem is a hardware issue (ie xp isnt quite compatable with your motherboard) you will get a blue screen error when you reboot after making the changes, this can usualy be sorted out by rebooting pressing f8 during boot and selecting 'last know good configuration' but not always