My KT7-A is killing me!

My system freezes after reading from a DVD for a certain time (e.g. when watching a movie). This is how the system looks like:

- KT7-A Rev. 1.0
- 300W HEC power supply
- XP 1700+ @ 1400MHz (Prime stable)
- 1024MB PC133 SD-RAM (2 x 512MB)
- 2 IDE hardrives, each ~15GB
- Toshiba DVD-Rom drive
- Gainward TI-4200 (128MB)
- SoundBlaster PCI128 (PCI slot 4)
- internal USB controller (PCI slot 5)

I've put the SoundBlaster into PCI slot 4 because I've read that some SB Live! owners were able to fix stability issues by doing so. Looks like that didn't help, though, as the system has just frozen again (after one hour of reading a divx movie file from a DVD).

HELP!