This happened to me last night; I was planning to send an e-mail to someone via www.classmates.com and the mouse wouldn’t move the cursor. Even when I hit Ctrl+Alt+Delete to escape, the computer did nothing. I had to switch the power off.
I have a flat-top Compaq console, with Windows 98 Plus! and a 1-gigabyte capacity.
It is probably a conflict between your display driver and another device or application. Go to the Compaq support site and download the latest driver for the display adapter in your computer. Or, for a quick and dirty fix, go to start/settings/control panel/display/settings/advanced/performance and move the hardware acceleration slider from full down to basic. This will take care of most driver conflicts, but it will impact graphics performance if you play a lot of games or other graphics intensive applications. It won’t impact most webpages or email though.
Thanks. I’ll try that the next time it happens. 
Alternately, open your computers case and make sure all the fans are working (give it a good dusting at the same time). If youre machine freezes up at random intervals, something may be overheating. Also, make sure your video card (and all other cards) are firmly seated.
Of course, if this only happened to you the one time… well… shit happens. Reboot and move on.
Wow, my typing sucks. Well, shit happens.
Good idea, Bryan…however, I’m quite reluctant to open that case at all, knowing I run the risk of screwing something up…
Sounds like summer heat, very common, each year in the summer there are alot of posts on it.
This is what I do. When it happens push the Caps Lock key & see if that light for it comes on, if so, the computer is usually busy doing something so wait, if not, restart.