Love the site! First time post!
My wife has a Dell Dimension 4600 (~3 years old) that is running Windows XP SP2. Over the last several days it has started completely freezing up (no mouse, keyboard, or other control) -- only choice is to pull the plug. She said this first happened while she was reading email and web browsing. I tested it several more times since then and it each time it froze shortly (10-30 sec) after loading windows and showing the desktop. IMPORTANT: it froze without ANY user input on my part -- I was just moving the mouse around and waiting for everything to finish loading. A few other times it has worked fine for a while then froze up while my wife is using it. We have not made any hardware changes, but I'm not sure what she may have done software wise.
After pulling the plug and restarting, I've frequently gotten an "unmountable boot volume" error and have to run CHKDSK to fix it. I'm assuming this is a symptom from having to pull the plug on the machine.
I'm not sure if this is a hardware problem or if I have a serious malware infection. I'd be happy to take this issue to the Malware Forum, but I was hoping someone could narrow it down first.