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.