I bought MS Office 2007 Home and Student over a year ago. I need to get MS Access but it sells close to $200 by itself. I could get Office Professional for only $80 but the Home and Student version that I bought has 3 licenses, of which I'm not using 2. Is it possible to sell the 3 licenses and get the version I need? Or is it possible to just add Access for very cheap? What's the best way to do this?

There is no way to sell your licenses, unless you sell the whole product. The license are only for your use.

You would have to buy access separately or purchase another version of Office that has Access with it.

If I sell the whole product, what happens to the license that I am using? Can the person I sell it to still use that license if I have already activated it?

You should not have a problem as long as you completely uninstall the software from your computer and it is not an OEM copy of software. If the person who buys the software from you has any problems with activation they could use the activation by phone method to talk to someone and explain that they bought the software off of you.

But to be on the safe side I would read the EULA that came with your version of software.

* This is my personal opinion on this matter and to be completely sure you should contact Microsoft for a definitive answer.