SO if you want to run crossfire on vmware i suggest you to use windows 7
Now the problem is how many cf you can open, this depends on your cpu and ram.
if you have a dual core cpu you can run one crossfire as bot but you can try it with two but it will be VERY laggy.
if you have a 4-6 core cpu and 8 gb ram you can run 8 bots
and windows 7 it takes 15gb for install[or less i think]