dev.karam 
So replace the broke down Dreamcast, it's just a recommendation and better than you breaking your PC by over heating it, but if you don't want to do that, then emulate it instead and put up with faults and hope you don't fry your CPU or GPU.
I already had known that, that is why I recommended NulDC in the first place, for tomb raider like I said just play the playstation version instead that works including smooth video playback.
The problems are with Demul that is a very good emulator but not without it's problems as is NulDC for that mater.
The video driver depends on your graphics card and what that supports, it's possible that some drivers are targeted for n-Force cards rather than what you have.
Dreamcast emulation has a long way to go yet before anyone can call it a replacement for the real console
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