Jay that is a pretty old and low end computer.
PIII and 600Mhz probably jsut wont work for AHII. You are not going to be able to run a high end (or even mid range card) with that system I'm afraid. There just isn't enough processor there.
Also, WinME is not exactly game friendly If I recall correctly.
Does your other computer have better specs? You may be able to update that one instead?
Sorry for the bad news ;(
Cheers,
RTR