Newbie user name problem

Hi everone
Am new to all this but even so this is an embarassing problem !

Installed WP a few days ago using WAMPSERVER on my PC until i get the hang of things,its all working ok but…..had some time this morning so thought i would play around with my WP site but tried to log in with what i thought was the U/name and P/word when I set it all up but its saying invalid u/name ????!!!
The P/word I know for sure but the U/name has got me, I was under the impression i was using the default one when i started it all the other day.

How can I find my U/name, without scrapping everything and starting from scratch again ?

thanks if you can help