How do I disable iTunes Home Sharing without deauthorizing the wrong computer?

How do I disable iTunes Home Sharing without deauthorizing the wrong computer?

A friend guessed my iTunes password and turned on Home Sharing through iTunes. I unknowingly logged in looking for some information, this re-associated my password with my friend's email address. I found some information about de-authorizing a computer, but it looks like this would remove my access to my iTunes account, not my friend's. Please, can anyone help me fix this issue?