I am experiencing a problem with my home computer and have searched on
the Web for a solution but can find no mention of this particular
issue.  After continued use (online or otherwise) the following
occurs:

1. The computer freezes for a couple of seconds
2. The sound of the fan (or whatever is whirring inside the computer)
increases in volume
3. The screen then goes black for about 1 sec
4. Everything comes back to what appears to be normal, yet I can no
longer scroll (either up/down or left/right) in any window.  What
happens when I try to scroll is very strange: everything within the
window gets scrunched up as the newly visible information is displayed
yet the old information doesn't move.

This used to happen only after hours of using the computer or after
using it to play back video or perform other memory-hungry tasks. 
More and more it is just happening out of the blue, sometimes after
only a short period of use.

It's interesting to note that:

1. Restarting the computer will always fix the problem (temporarily,
of course), which tells me that it is not an issue of the computer
overheating (how could it cool down so quickly with only a restart?).

2. Sometimes it skips the freeze/whirring noise/blackout and just goes
straight to the scrolling problem.

My question is: WHAT IS CAUSING THE PROBLEM AND HOW DO I REPAIR IT?

System information:

Intel Pentium 4 CPU 2.40GHz
512 MB of RAM

Microsoft Windows XP
Professional
Version 2002
Service Pack 2

Thanks!

It might be useful to know some more detail on your system.
Motherboard and Videocard, etc.

Some things you can try:
 - Test your memory. Well, your computer's memory. ;-) I recommend
memtest86+ from www.memtest.org.
 - Have a look at your mainboard. Check that the memory and video card
are seated properly (actually, check everything while you're there).
Also check the capacitors on the mainboard. If any of them are bulging
(or worse, leaking) you need to replace the mainboard.
 - Try lowering your video card's accelerator settings (Display
Properties > Settings > Advanced > Troubleshoot).

Thanks.  The video card is:

NVIDIA GeForce4 MX 440, 128.0 MB

Your video card is the problem. 

GO to the NVIDIA website and try to update the drivers in the
downloads section.  If this does not fix your problem change your
video card.

 With regular usage, video cards can ?burn out?.  It is a simple fix;
purchase a new ?AGP? video card.  Check the specifications to
determine you minimum system requirements.  Consult the installation
instructions.  Open your computer, carefully remove the old card, and
install the new.  Update the software with the included CD.  This
hardware should automatically function.  This should fix any problems.
 All directions on installation are included with the purchase of the
card.  I had an extremly similar issue.