PCI-E works just fine in win9x, no additional drivers required. It's more or less like PCI on steroids.

So PCIe and AGP are only a matter of performance? I'm not trying to run Windows 9x anymore in this machine, I just don't want to find out that some game used some AGP specific thing that will make it not display correctly with a PCIe card. I don't recall this ever happening to me back in the day, but I'd like to be sure.

Games that support AGP features will act as they are running with a PCI video card. No game ever required an AGP to run.

So there are some features that AGP has that games can use that they won't use if I go PCIe. Are these performance related, as in, will I be missing out some graphics stuff if I go PCIe?

Mostly "AGP Aperture Size", which allows extending texture memory to system RAM, so games can use much higher-resolution textures. G-Police for example uses these if it detects an AGP card. If you use a PCIe card, which has way more video memory anyway, it probably doesn't matter.

Nice. That's what I wanted to know. Thank you.