Alright, so I've recently developed a problem with my desktop computer. Whenever it is left on and unused for a while it will lock up completely, on whatever screen is currently up (no BSoD). Sometimes the cursor will still be movable, sometimes it will not. Also, seconds before it locks up I'll get a message from my wireless connection, telling me that the network connection has limited/no network connectivity. Then, it will freeze, with no error messages or other notifications that it has frozen, and it will stay this way until rebooted/turned off. Rebooting will cause it to work fine. At the moment I have no idea if the problem is caused by hardware, virus/malware, or something else entirely. My antivirals aren't picking anything up, but honestly I know that means little if its something serious. So I'm hoping one of the experts here at DAL will be able to tell me what steps to take to discern and hopefully solve the problem.

My System Specs Are Currently:
Motherboard-ASUS P5Q-E
Processor:Intel Core 2 Duo CPU E7300 @ 2.66GHz
RAM:2GB of Kingston DDR2 (single-channel)
HDD:2 1TB Seagate Drives
GPU:ATI Radeon 5770
OS: Windows XP SP3

If any other information is needed, just let me know.
Thanks, guys.

Whenever it is left on and unused for a while it will lock up completely

So, it only happens when you are not using it? Is it consistent?

Well, in every instance except one, it occurred when I came back to my computer after having been away from it for some time. I would turn the monitor on, everything would look normal, but then I'd notice that even if I had a mouse cursor I couldn't click on anything at all. As to the consistency, it doesn't happen every time I leave my computer alone, but it only started a few days ago, so there haven't been a lot of opportunities for it to do so.

I am trying to discern a pattern, such as when it goes into, or comes out of sleep mode.

So you say you turn the monitor on. Does that mean you shut the computer off, and this happens when you power on? Or when you wake it up?

Neither, actually. Sleep mode is disabled on my computer, and this only happens when it's on. Essentially whenever I go away from my computer I turn my monitor off, but otherwise leave the system running fully. When I come back, it has locked up, and disconnected itself from my wireless network. I don't think it so much freezes as has all its resources used at once, as occasionally my Zonealarm toolbar icon will flash, or my network connections manager, indicating that they are still running, albeit extremely slowly.

Hmm, that is odd. How much time are you talking about? And has it locked up while you were using it? Did you recently update any drivers or make any other changes?

It's locked up three more times in the last two days. One of them happened when I was away from my computer for about five minutes, and the others while I was away from the house for hours. It seems to be triggered by inactivity on my part. Perhaps someone taking over the computer when its not in use? When I come back to a locked system I notice that there are about 8 network connection icons in the taskbar, and the wireless card seems to continue to be active. But I haven't really made any hardware or software changes recently, so I'm not sure what triggered it to start locking up originally.

Perhaps someone taking over the computer when its not in use?

Well, Windows certainly does things when the user is idle. What security software do you use? You might do some supplemental scanning with Malwarebytes's Anti-Malware (MBAM).

Unfortunately for security setup I've only got the barebones of avast! and Zonealarm in place. They don't seem to be coming up with anything, but then again they hardly do. Also, I just had the system lock up while I was using it. I got the Task Manager up before the system completely locked, and it was putting out a consistent CPU usage of 100% after the point it locked. However, I didn't get a chance to switch to the processes tab before the Task Manager also became unusable.

Unfortunately for security setup I've only got the barebones of avast! and Zonealarm in place.

A respectable anti-malware and firewall are hardly "barebones", but are key elements of a good defense. As long as you have kept them updated, as well as keeping Windows updated, AND you avoid risky behavior, most notably illegal filesharing, security should not be the issue. Still, it might be a good idea to have one of our malware removal experts take a look just to be sure. Please read this then start a new topic here, then come back here when done with the results.

You might check out Process Monitor – an advanced monitoring tool for Windows that shows real-time file system, Registry and process/thread activity (combines and replaces two legacy Sysinternals utilities, Filemon and Regmon). It is like Task Manager on steroids.

If it did while you were using it too, I would start to look at other issues, like RAM or a failing PSU, but since it only seems to happen when you are idle, it sounds like something is running on your system.