I am not sure what works with backtrack3 you would have to check their site but you can get a solid card for pretty cheep these days. My current notebook has an intel chipset and it works fine.

Basically there is an extra "mode" that has to be able to be utilized - monitor mode. A lot of people think it is promiscuous mode but it is not. Monitor mode unlike promiscuous mode does not need to connect to an AP to sniff packets.

- You probably want to try WEP first, it is a lot easier
- I think VMWare only allows you to assign direct access to some USB devices which may be limiting
- The more traffic on a network = more IV packets so a clientless (passive) attack may be difficult, in this case you can help push it along actively by using a deauth attack
- I think it is something like you need at least 50k IV's for 64bit WEP and 250k for 128bit, you may want to look that one up

I think that's about it - good luck - have fun