If your going to go as far as upgrade your CPU, GPU, and Memory why not just get a newer low end computer? You can find computers with stats like 1 gig of ram, dual core amd (4000+, 4200+ lower end ones) and a 7 series nivida card for under 600 or even 500 bucks.
Its probably worth it to hold out and get a new computer for you becuase of how old your setup is.
And you didn't know how to find out what your GFX card was, and easy way is to go to Start > Run > Type in "dxdiag" and view your display information