Pci and agp...need pci express...?

Okay, after spending forever learning about the pci slots in my computer, I've figured some stuff out, and I'm not happy about it. I'm pretty sure I have four regular pci slots. I have one agp 1.5v slot(which I'm not entirely sure what that means...) My graphics card died, and I'm looking for a new one. I found a very, very nicely priced card that I was very happy with. I almost bought it, untill I got to looking at the little slots on the bottom. It is a pci express 16x... I'm not sure what that is, but I know I don't have it. Is there any way I can either adapt or just somehow get a pci express 16x slot without getting a new motherboard?