If you have a fairly decent AGP rig, with say a 3400+ or 3.2GHz Pentium 4, it's a tough situation to be in, as upgrading will likely involve throwing away most of the components in your system. DDR has moved to DDR2, AGP has moved to PCI Express and most of the CPU sockets have changed too. If you have a Socket 939 AGP system, it's not quite as bad, as you can buy a newer nForce4 board for under £60, but this is a fairly rare situation to be in.