Figured I would post this as there may be others looking for an answer and the 3 Apple stores I called were clueless. I have a 2011 MBA with a thunderbolt port but a 2010 iMac with a mini display port. I wanted to connect my MBA to my iMac and use the iMac as a display. The first Apple store I called told me it couldn't be done. The 2nd one told me they didn't know and the 3rd told me i could use a thunderbolt cable. So of course the thunderbolt cable didn't work. Took it back and called Mac Mall. They knew right away what I was talking about and told me I need a mini display to mini display cable. Luckily they had one and it works perfectly. Just thought I would share in case others wanted to know if this could be done.