Best release for me?!

[grimbob]

First off i'll apologise for this post, I know they must be annoying!

My system specs:
AMD Athlon XP 2100
Asus A7N266-WM
768mb ram
running on board lan, sound, and video.
Currently running Vista, want to get rid of that and just run Mac.

Any help on a good leopard release for me it would be very much appreciated, not sure even if I can