MSN and google...

so, i started talking to someone on MSN today... and im concerned.

He was able to somehow, would NOT tell me how, find out (not sure what he looked at) my internet name (not real) my username on forums, my birthday... basically im worried about my security on the computer.

how can i stop this from happening? how did he get this info in the first place? my name and bday are probably on my MSN profile... but my forum nickname is totally different... (not the one used here).

im worried. could someone help? Im worried what if he might get into more things than i know of?

ive since blocked him on MSN but, hes already got the info...