Play descent and descent 2 in windows with a source port
http://www.dxx-rebirth.com/

I know about source ports obviously. There are people who prefer to play the games in their original form if they work... If anybody would only use source ports and DOSBox this (sub)-forum wouldn't have much purpose, now wouldn't it?

and source ports with a Voodoo card is a bad idea because of the texture size limit anyway

Here's a few things which might help if you didn't already check:

#1 What drivers are you using? Drivers can cause weird errors like that (such was the case with some cards I had, ATI Rage *cough cough*).
#2 Is the card properly cooled? Excessive heat can agitate GPUs in that manner.
#3 Do you have a well shielded VGA cable? Sometimes poor shielding can affect image quality.
#4 Does the monitor support 320x240 & 640x480?

I have seen some horizontal tearing with voodoo 3 cards, but it is all over the place when it happens. It happens when the voodoo 3's clock is set to low, and it also depends on the systems FSB Bus speed. But I don't remember if a faster bus was more or less likely to make things tear...

But your voodoo is already clocked high, so that shouldn't be a problem.

Running latest patch already? I think it included a Win9x .exe and it's not from 3rd parties.

Thanks for the further suggestions... I tried it with a 3500TV since (newest stock drivers) and same thing. I don't know if the monitor supports the proper resolutions, but Eizo monitors are some of the best around overall so I'd be surprised if it's the culprit. As for the updated W9x .exe, can't try that cause I only have the shareware version so far.

Wasn't there a 3dfx version too? Some shareware titles came out with 3dfx versions. Maybe in Glide mode the problem will go away.