Yes its true that your internal wireless will not be found inside a VM. The VM will only have full access to a wireless card that is a USB device.
You 'could' mess up your operating system by installing BT on your harddrive, but only if you do not know what you are doing... And seeing as how your name is what it is, I'll assume that you will mess up your system if you try.
Yes, IF you install to the harddrive you will see your internal wireless card.
My suggestion? Run a LiveCD instead of installing it, that way you don't break your 7 machine and you can still use BT4.
Seeing as how your other post was a little... Fuzzy with your ethics this might be the most I'm willing to help you with.
Link to fuzzy ethics: http://www.backtrack-linux.org/forum...tml#post157921