Sounds like you've run out of memory perhaps...
I would look at boosting your PC's RAM.
Also, look at your Virtual Memory amount and consider changing it.
Before you even consider what virtual memory is, I want to make one thing clear:
Although this won't make your machine explode into a billion small pieces, it can be quite dangerous, so be careful.
1: Go to your Start Menu
2: Click on Control Panel
3: In Control Panel (in advanced view in XP) choose 'System'.
4: You'll notice some stats about your computer at the bottom. Note the amount of RAM on your PC (some may have been reserved for onboard graphics).
5: Click the 'Advanced' tab at the top.
6: In the 'Performance' group, click the 'Settings' button.
7: In the 'Performance Options' form just opened, click 'Advanced'.
8: Click 'Change' at the bottom of the screen.
9: Your 'Virtual Memory settings should be about 2-2.5 times the amount of RAM on your system. So, for example, if you have 512mb of RAM, then having 1024-1280mb of virtual memory is normal.
Please be aware, that for this to work properly, you will need a couple of gigs of free space on your hard drive for this to work.
10: Press the 'Custom size' radio button.
11: Enter a initial size which is approximately 2x your available RAM ('available' meaning, if you have 512mb, and 32 reserved for graphics, then your available RAM is 480mb).
12: Enter a maximum size which is about 2.5x your available RAM.
13

ress 'Set'. A wait may occur while the system re-configures.
14: Press 'OK' and exit all of the system tabs.
You may need to restart your computer for the changes to take effect.
Other things which could be done are:
<LI>Defragmenting the hard drive on a regular (weekly) basis.
<LI>Removing any excess porn videos on your hard drive.
<LI>Buying a better PC.
Hope this helps.