Hello,

We recently received some copies of MS Office Home & Business 2013. Inside, there is a card with the product key and instructions to enter the 25 character key @ office.com/setup to obtain the setup files. It asks you to sign in with a Microsoft account so I used a personal on I had since the company I work for doesn't have one, but unbeknownst to me, the product key was assigned to it.

Is there a way to unassign this key or transfer it to a different e-mail account? Obviously this would create problems should they need to reinstall this software or I leave the company someday.

You've posted in a Microsoft Exchange forum.  I recommend that you post in an Office forum.