So how did you find out there was a problem?
On day I was looking through the display settings, I forgot why, but I noticed in the nVidia tab of the display settings there was an "Adapter information" setting. It said my card was set to PCI mode. I thought that was odd, so I opened up dxdiag and went to the "Display" tab. Sure enough, AGP Texture Acceleration was disabled.
I did a quick search on the internet and found out that sometimes the AGP drivers aren't installed automatically. If you search google for "AGP drivers", the second link is to Intel's AGP drivers. I downloaded their driver package and boom, I'm at AGP 8X now.