Welcome aboard, Banger.
When you installed SuSE you should have been prompted to give a username and password - effectively 'creating a new user'. It is this username and password that you should enter here. As it stands, since (I presume) you're not connecting to a Windows domain, your SuSE setup shouldn't know anything about your Windows users.
If you can't remember creating a new user, then try using the username "root". You certainly should have been asked to give the "root or administrator" a password. This "root" user is the Linux/Unix equivalent of the "Administrator", except you have the potential to wreck even more things. Only use root if you absolutely have to.
Since you haven't even begun to play around with SuSE yet, if you can't remember creating any users and you can't remember giving any passwords, then go ahead and re-install SuSE again and make sure you read absolutely everything on screen at least twice and make notes