No - totally different architecture there. PCIe is a nice idea, but at the moment it's only really worth upgraing to it if you're going down the sli route. For th most part you'll see no difference between agp and pcie perfromance wise. Eventually it'll be worth chaning, but by the time cards come out that exploit the advantages of pcie, today's processors will be too slow to cope with them.
Canith - it's possible that you motherboard won't have an agp slot. If it does, it will be brown, kind of set in the middle of your motherboard, just above your pci slots (the long beige things). If you can post back with your pc make and model number (or preferably your motherboard make and model) we can see what you have. Also post you pc's specs and we should be able to recommend a couple of cards.