serial number already in use - but not from me - I have the legal original copy here

Hello,

how to solve this problem? I have a legal copy of photoshop elements 12 here (i need exactly this version due to the hardware setup), but in my account, it says that the serial number is already in use.

Is there any way an admin can "reset" this or how can I proof that I have a legal cop here, holding it in my hands right now?