Your saying minor gaming?
If you even plan to leave the desktop your going to want at least a 9600pro, which can be had for $100 at newegg. (thats the budget solution)
For give or take $175 you could get a Nvidia 6600GT which would allow you to do any minor gaming very well.
You already have a 3.2ghz northwood, and it would be pointless to purchase a low end graphics card for such a nice cpu.
See I am still not sure what sort of money your looking to spend...
lets assume that you have $400 left to spend??
you could pick up 2 sticks of 512mb pc3200 from Wintec off of newegg for $37 each with shipping.
As far as your optical drives go, you can get SONY cd-r drives for as low as $30, and generic ones for even less. I never over spend on optical drives.
A good brand hard drive like Western Digital, running at 7200rpm, with 160gb capacity is usually around $90 also.
You can build a pretty nice system, pretty cheap. Once again, with more information, we can narrow down a build for you. I just tried to build you a system that was very cost effective.