Serial number register to another apple id
I bought my macbook pro from the apple store in mid 2010, and set it up using all my own apple ID and info. I just found out about registering my apple product with my apple ID, so I tried to input the serial number into my apple ID on supportprofile.apple.com , but it says it was already registered with another apple ID. I had only 2 apple ID since the beginning and I tried both, but none of them work. So how do I find out which apple ID my serial # is registered to, or is my macbook too old to be registered?
Thanks in advance
MacBook Pro, OS X Mavericks (10.9.3)