Yep, email addy is the key, AFAIK. If ya ain't processed a completed WU yet, then it prolly won't show you under the stats with your old nick, but I ain't sure. Just change the nick on all the machines, and then wait for a few days to see what happens.
Or, if ya wanna know for sure, visit the FaD
forums and search for the answer.
Cheers
Mick