I'm on a Athlon XP 1.8 ghz, 1.5gb ram, a gfx 6600.

I have my alts capped at 4 fps and my main at 20 fps. I run 4 chars simultaneously, giving me about 11-12 fps in Outland at the dark portal :P
Anyway I just ordered a new computer so I will be happy to get rid of that ridiculus < 20 fps machine.
For me the RAM is enough, it's my CPU and GPU that is slowing me down.