If you've already got an email account configured in Windows Live Mail, you don't need to remember the details, as they'll already be stored in the program.
Are you, perhaps,trying to set up a new account or is it something different?
If you've got an account configured with Windows Live Mail then, depending upon your chosen settings, it should either automatically fill in your password (which is fine if nobody else uses your computer) or ask you to enter it. However your username ( = your email address) should be stored there already.
Perhaps Jordyboy meant 'password' instead of 'user name'? (If so, my question still stands: Who provides the email service? i.e. what's after the @ in the email address?)
If you know the whole of your email address and your password, what is it that you've not got for Windows Live Mail. If you don't know the first part of your email address, how are you able to get into Web2Mail?
I'm probably just being thick (no change there,then!) but I obviously haven't quite grasped your problem yet!
PS:
Normally with email clients (such as Windows Live Mail) your 'username' is either your full email email address or just the part in front of the @ symbol.
If it's just your email address you've forgotten, the best way might be to ask someone you know that's had an email from you recently. Alternatively, if you've used this email address to sign up for other websites, you should be able to go to those websites and see your details, if you're still logged in to them.
^^^ Even simpler, if the email address you're trying to remember is the one that you used to sign up to AB, simply click on 'My Profile' and then on 'Edit My Profile'. Your email address will be displayed there.