Who is Riddle to Harry?

Mon Oct 21 05:00:24 UTC 2002

No: HPFGUIDX 45617

In CoS, "while Harry was sure he had never heard the name T.M. Riddle 
before, it still seemed to mean something to him, almost as though 
Riddle was a friend he'd had when he was very small, and had half-
forgotten."

It would seem that Harry did have some kind of relationship with Tom 
Riddle before losing his parents.  When, though, did Riddle switch to 
the name "Voldemort"?  Wasn't it long before the Potters married?