I found a way to do it... though it sucks it's still better than nothing. Go in the video option and switch to software mode (don't bother changing the other settings, it temporary) then alt tab or ctrl alt suppr (both works, but i couldn't alt tab myself) do your things come back to the game, switch back to 3dfx mode... I would advise you set your resolution inside nglide's configurator if it's not already done.

For Windows folks who can't find the "suppr" key, use ctrl-alt-del and run the task manager. Be warned, though--whatever you have to do on the desktop will be in cramped 640x480 using this trick, in Windows. Click the task on the taskbar to get back to the game.

Actually, I think the 8-bit color mode actually looks better than 32-bit in some cases. For example, in the Thieves Guild stores, the 16 and 32-bit modes show the wrong colors--bright pink spots on the walls, for example, and a sickly greenish yellow hue from an otherwise comfortable-sounding fire. But in 8-bit color mode, the room flickers lively and homely as one may expect an underground shop to be when lit up by one crackling light source, and there are no strange pink splotches on the walls anymore.

The game also seems to generally load a lot quicker in software mode for me.