Ok, you need to get that motherboard I suggested to you. And no, your Radeon 9250 is NOT PCI-E. The Radeon 9250 was never made in PCI-E, only in PCI and AGP.
Your Celeron should work in the Socket 478 motherboard. Or, either that or you have a Socket T (LGA775) or Socket 370, which is EXTREMLY old. They don't even make Socket 370 anymore! Infact Socket 478 is going obsolete too. But anywho, you either have a Socket T, Socket 478, or Socket 370 motherboard.
Unless you want to really get that nVidia nForce4 SLI motherboard, then you have to get a new video card, new CPU, and well, pretty much new everything.