System with dual display freezes

I have just finished adding a secondary display to a friends computer, and every now and again it will freeze up.
Things that make the computer freeze is maximizing Microsoft Word windows, or playing MP3s for over 1 hour.
I have been trying to fix this problem for two days now, and the only thing that I can think of it that might be a problem is the secondary video card doesn't have an IRQ for some reason, or maybe heat problems could this have something to do with it?
The system specs are:
Dell Optiplex GX150
Intel Pentium III 1 Ghz
128MB RAM
20GB hard drive
Primary display: S3 Trio 64V (Dell E551 monitor)
Seconday display: Cirrus Logic 5446 (Generic monitor)

Thanks in advance.
Yuri.

Playing MP3 files for hours may be your clue. Thats a lot of stuff loaded into memory at one time.
You might want to check systems resources in Windows Explorer>Help>About Windows.

The system resources when windows starts up is 93% after two hours playing MP3s the resources have gone down to 89%, but even maximizing a word window in the first few minutes of windows loading will cause it to come to a complete halt and nothing but the power button works.
Any clues?
Yuri.

*bump*