
Installing a PCI graphic card will surely boost the graphics but it is not recommended at all.

Firstly it costs a lot more as compared to its AGP version and secondly it won't give you the performance of AGP one.

I am guesing you have initial Pentium 4 w/ socket 423. Even if change your motherboard to AGP slot one and buy a new grahpics card, the memory interface of SDRAM will become a bottleneck in games. So you could consider another version of 845 chipset that supports DDR RAM but now you will have to change the RAM as well. So it is not justified to spend so much money upgrading on this system.

If you have cash then try and upgrade the core system to an P4 2.8 and above or AMD64 one. I know this doesn't sound too good in economic terms.

If you really are low on cash and cannot upgrade your core system then there is a PCI version of GeForce Fx5200 available (well under 6k). It will let you RUN all the games albeit at low resolutions and low settings of games.