What chipset does that mobo have ? AFAIK most of the Intel chipsets (if not all) were AGP 2X capable. For what I know, AGP 2x is still fast enough, using AGP 4x over it gives you ~1% performance increase (if any at all)...
Let me copy part of my reply from a previous post on this same question:
"...are you sure your motherboard only supports 1x? In fact, though I could be wrong about this, I think that any board that has an AGP slot supports 1x and 2x. Don't get confused by the specification: AGP 1.0 can do 1x/2x. AGP 2.0 can do 1x/2x/4x. Stupid, eh? Anyway maybe you should double-check that. I bet your board does 2x because 2x was included in the very first AGP spec."
Anyway it's worth checking into. Post your motherboard here if you need help figuring it out.