My
Computer Won't Shut Down Itself After Installing XP
There are a number of users who are noticing that their
PC will no longer automatically power down/shut off
without pressing the power off button on the computers
unlike in Windows Me/95/2000. There could be a number
of reasons for this - but the main one seems to be that
ACPI is not enabled on the computer or in Windows XP.
Here is how to try that out:
Click - Start - Control Panel - Performance and Maintenance - Power Options Tab
Then click APM - Enable Advanced Power Management
Support