XP intermittantly hangs during shutdown

Hi folks. Again with the strange and intermittant problems for me, it seems. Still running the box detailed in my sig, and Windows has started occasionally completely hanging up when I tell the computer to shut down.

No real symptoms; I close all programs, wait for the hard drive to stop being active, and commence a shutdown normally. What happens is that once in a while I issue the Start > Shut Down command, the hard drive churns for a minute, and then everything just sort of stops. It never makes it to the 'Windows is shutting down' screen, the mouse moves but nothing responds to any input (mouse or KB), and it takes holding the power button to kill the system.

Antivirus and malware scans are clean, the only change in software I've made recently was installing OpenOffice (and I started seeing this before I did so), Avast as a program is up to date. There seems to be no real reason for it, and everything I can find on Google is years old. I'm stumped, and I hate having to hard-crash my machine - anyone have more of a clue?

 

Before you shut down run Task Manager. The first time, write down all the processes running.
Then shut it down. If it shuts down properly, none of the processes is causing a hang.

The 2nd time right before shut down, again run Task Manager and only write down any new process running. If it hangs, one of the new processes is the culprit.

It might take you lots of looks in task manager before you figure out the process. But do run it every time before you shut down so you have a record of processes and good and bad shut downs.