If I recall correctly, AGP slots are brown and PCI are white...usually. If a motherboard (MB) has an AGP slot, ususally there's only one. As for PCI slots, they range from 2 to....I've seen 4 on a MB, myself.
Click
here to see what a PCI slot looks like...it's the top picture.
Click
here to see a picture of an AGP slot... the second picture.
And as far as I know, the chipset on the videocard really has nothing to do with the chipset on your MB. Just be sure that the videocard can handle T&L (transform and lighting). I think that's an AH2 requirement. All GeForce (Nvidia) cards from the GeForce2 and higher all have T&L. I'm not familiar with ATI cards to give you any info there, but I'm sure a quick search on these boards could help you out.
To get a very detailed output of what's on your PC and what you have configured, click on Start, then click on Run. In the Open field, type in dxdiag and press OK. Once it completes, you can save it as a text file by pressing the Save All Information button. That comes in handy if you need to send your PC's info for support.