I have run G2 on a 433 celeron before I built my new system so I would guess the AMD 500 should cover it. G2 likes a decent video card so I would guess that would be the problem area. Of course a decent video card of at least 32mb with full 3D support. A geforce 2 mx 400 is own to about $30 US at most places and a GF4 MX440 about $75 US.
These are not my top picks for a killer gaming rig, but G2 loves them.