Wow, that Pentium 4 needs to be upgraded STAT! What kind of motherboard do you have, is it from a Dell or HP or was it a custom guilt PC. If it is a dell or HP
, chances are you will not be able to upgrade the CPU and you will need a new motherboard. If it was a custom built PC, than let us know what motherboard it is so we can tell you if you can upgrade the CPU.
You will not be able to upgrade to a better video card as that CPU will be a major bottleneck.
If you have an AGP slot, the most powerful card that you can install is the Radeon HD 4670.. However, as suggested by everyone till now, You'll be better served by getting a new system.. IMHO, a 890GX chipset motherboard with onboard HD 4200 graphics is going to be many times better compared to your current video card..