Have you tried installing it or are you just assuming you cannot. You are normally allowed to install and activate on two machines.
You will need to contact Adobe support thru chat in order to get assistance with deactivating the inaccessible installation. For the link below click the Still Need Help? option in the blue area at the bottom and choose the chat option...
Serial number and activation chat support (non-CC)
http://helpx.adobe.com/x-productkb/global/service1.html