pc will not shut down

Clarifications

NT

If you do not have up to date virus protection I would go to trend micro's housecall online and run a scan. See what this brings up.

If that doesn't find anything I would open the case and take the hard drive out, get a hard drive enclosure plug it into a different computer and scan it with a free program, and a root kit revealer.

If that doesn't work you could always nuke and boot your computer, and then re-install the operating system. If you do that don't forget to back up all of your information before hand.

Let us know how it goes.

I might try going to "Start" > "run" > type devmgmt.msc > go to Network adapters, right click on your adapter, Properties, "Power Management" tab (make sure everything is unchecked), then go to Advanced tab > "Wake Up Capabilities" or something like that... and set it to none.

Give that a try... might work.

Check your Event Logs and Minidump files

Windows XP restarts unexpectedly or restarts when you shut down the computer

http://support.microsoft.com/kb/320299/

A couple more tips here

http://www.kellys-korner-xp.com/win_xp_restart.htm

adding to post above about the wake on lan option....though it may not show it in the windows devices.msc, you may want to look in the BIOS of the system and make sure that wake on lan and wake on ring are both disabled (wake on ring may not be there if you do not have a modem built into the system).

Disconnect Ethernet (network) cable and see if that stops the reboots. If it does, we can proceed from there.