Hello Slotguide1,
1) Yes, you can sell your copy of Vista IF a) The copy of Vista is a Full Retail version (not OEM) and b) That copy of Vista is Not installed on any system
2) False, you can install a Retail copy of Vista as many times as you need as long as it is only installed on one computer at a time.
(NOTE: When you Activate the first time, it can be done over the internet, but any time after, the user is required to Activate by Phone. Therefore, I suggest that you inform the person that you sell this Vista to, that if they try to Activate over the Internet they will receive the error similar to "Key already in use". They will need to Activate by Phone and talk to an Activation Rep.)
Thank you,
Darin Smith
WGA Forum Manager