I imagine that you have an LX based board. LX does support 2x AGP (there was never an Intel chipset that supported less than 2x), but it might not work with the more fussy AGP cards. One main problem with motherboards of that period was that they couldn't supply the power required by the AGP card - that's the most common reason for failure, not the AGP features support.
But I did have an AGP Rage Pro card with an LX board, and a friend of mine has a TNT card on an LX board, so there's a chance that a card you'll get will work. But it's best to try before you buy.