[color:"orange"]Gateway doesn't name the board itself except by it's Gateway part number - my computer system info is telling me it's an Intel D848GRG.[/color]
The system info program may be guessing, or it is a custom version of the board that it can not distinguish from the standard version. Unfortunately, Gateway's info is probably more accurate.
The AGP slot would be just above the PCI slots, lined up with the top slot cover at the bottom back of the case. At first glance 'AGP slot' and 'AGP interface capability' appear to be the same thing, but the latter may just be a fancy way to say they hardwired a chipset into the AGP interface, without the extra stuff to allow it to be replaced with an add-in card.
You don't need to worry about upgrading the power supply if you are not adding a video card. I'm not sure if anyone makes a PCI version of a card with Pixel Shader 1.1 support. Actually, the reason the AGP slot was disabled was probably so they could get away with using a minimal power supply (and it is probably cheaper).
