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Use DGvoodoo

extract contents of 3Dfx > x86 folder to IGI root installation folder
extract contents of MS > x86 folder to IGI2 root installation folder

extract dgVoodoo.conf and dgVoodooCpl.exe to root installation folder

run DgVoodooCpl.exe

General settings > Scaling mode set to stretched

Direct x settings > Resolution: 1920 x 1080, Antialiasing: 8x, Miscellanneous: Force V sync

Everything else left at default.

Game works great now. Make sure to lower mouse sens in game, doesn't like precise mouse input on high sens
Good for you you got it working.

By the way you can ignore the 3dfx files as you don't need them for this game.