General pci-e question?

hey guys im back with a very noobish question regarding the difference in pci-e and pci-e 16x. Can some one please explain the difference partaining to a very hypothetical situation. Lets say i wanted to eventually run 2 radeon 4770 in crossfire mode. i know that i would have to have at least a mobo the allows that set-up,but my question is can i use 2 pci-e (not pci-e x16) to run that particular set-up? do i even have to have 2 pci-e x 16 slots to run crossfire? sorry for such a noob question but un fortunately thats what i am right now.if anyone can suggest a mobo that would run this set-up and preferably one that will except an intel chip that would be awesome.

thanx for the heads up im pretty much new to this whole building ur own rig deal. ive already purchased one radeon 4770 for the time being i have a gateway 503gr with a wolfsburg edition mobo and a pentium 4 processor i bought a 500 watt psu but it looks like i wont be able to fit it into my case i guess i should have thought out this whole process before i opened up my check book!