Windows not loading; new videocard

Hi guys, I recently bought a GeForce 2 MX 400 and decided to put the Diamond Viper V770D (TNT2) it was replacing inside my older PC, a Pentium II 233. I used the Standard VGA setting in Windows (98 SE, btw) so I could make a network connection to the other PC where I had the latest nVidia Detonator drivers. I installed the drivers and from that point most of the time when I boot up now all I see is a green screen flash, then nothing... I managed to install DirectX 8.0, but that didn't fix it, either... what to do? Thanks again guys.