It is Windows, and I'm at the person's home right now. When I first got on the computer I saw the symptoms - I was at the login screen, and when I tried to enter the user's password to log in, it wouldn't show the keypress, and was generally acting strange. I was able to log into a second account, though. Once in that account, things were not normal yet - I still couldn't type into things like the search bar, when I hovered the cursor over the taskbar it would turn to a text cursor instead of an arrow, and the start menu wouldn't open. Also, double-clicking on the Firefox icon on the desktop would open the properties for the shortcut instead of the browser.

However, about two minutes after logging into this secondary account, everything started working normally again. I then restarted, and was able to log into the main account like usual, with no problems whatsoever. I've since been looking through the computer trying to figure out what might be causing this, but everything looks normal! msconfig shows very few startup programs at all, and none of them are suspicious in the least. A HijackThis! scan shows a fairly short one-page list with nothing unaccounted for. And of course, a virus scan finds nothing more than stuff like temporary internet files.

I want to tell the user that it's working fine for me and that I can't find anything, but that's what I told him the last time. He says that everything worked fine, but "if I work on it for two hours it starts acting weird, delays my keystrokes, and looks like it's trying to open programs." I don't know what that means.

Any ideas?