Computer is locking up after being idle

I have an hp pavilion a1510n. I recently wiped windows media center and installed xp pro. Computer ran fine for several days. I installed Norton antiviris corporate version 10.2 and a day or two later the computer started locking up. The Mouse and Keyboard are not locking, however, I cannot get access to the start button or any applications from the desktop. The computer can be shutdown manually and rebooted and everything works fine. I can sit at the computer and work for several hours and/or surf the web, etc and no problems. If the computer sits for 20 min or more idle then it will lock. I have checked the display settings, hibernate is disabled and sleep or standby is turned off. I uninstalled any other viris and firewall programs and I have uninstalled Norton and still the computer locks after 20 min of idle time. I don't know what to do next. If anyone has any ideas they would be greatly appreciated!

Thanks for your Help!
Melissa

If you hadn't said that you had uninstalled norton I would have said that it is configured to "scan when idle" idea being, worker gets pc scanned when they go for lunch. If you have a lowish spec machine that will make it seem like it's in real trouble.

Did you get rid of Norton totally? Any other AV solution on the machine ? If KB still working, CTRL+ALT+DEL and see what task manager is upto and what processes are hogging. If you can't get that, get task manager up and then let it go idle to see the offending application.

Maybe also check control panel / power options to see what it going on there.

These are just a couple of known things that can react when the PC goes idle.

To totally discount any software issues, I would wipe the disk and reinstall XP especially if you haven't got a lot of installed apps and data. If the problems still persist, you could start looking at the hardware.

I turned on task manager and watched for about twenty minutes until right before the system locked up two things popped up in processes: dfrgntfs.exe and defrag.exe. Anyone know anything about these? So far most say it is a windows file, however some say that spyware, virises, etc sometimes use or hide under the dfrgntfs.exe name. How do I tell the difference? Any information or suggestions will be greatly appreciated.

Thanks again,
Lissie

The post in the following link sounds similar to what you are experiencing:

www.ozzu.com/ftopic35589.html

K

Useful link by KiLLaBeE. I've however never heard of Defrag running automatically unless a Defragmentation utility like Diskeeper is installed.