Retrieve P5 key for Upgrade

I am upgrading from 5 to 7 since I installed Lion but it is asking for my v5 serial key and I cannot find that. Is there any way to retrieve it from within the software or something? I searched the knowledge base but didnt see anything specifically answering this.

 

i looked in the XML file using KB: http://kb.parallels.com/5680 and using that key P7 states that that specific key is not valid. I have never had any other installation of Parallels on this machine so that must be the only key I have ever used. Please advise.