I can't find any good pics of the inside of your system. You're going to have to replace the power supply on such an old system. I recommend sell your system intact after doing a fresh install of windows, and get a full size case, such as the antec 300 so you can run any atx or micro atx board you desire. Build your own with windows 7. If you know how to change a board, then you can finish any new build. Here's a video from youtube: http://www.youtube.com/watch?v=gKgK8Z8Z7-o&feature=related.
o1die, thanks for the prompt reply though i don't have that budget yet. i thought i'd just settle for a motherboard that can use the existing processor (with the appropriate new processor to come later) and the ram for such motherboard.
A new motherboard for your current ram and cpu won't improve your performance, and won't work with your original windows installation. It's a waste of money. Save your money and do the upgrade all at once: new cpu/board/ddr3 and power supply.