Computer talk

C is your hard-drive, in other words the "mind" of your computer. "Username" is your name or whatever pseudonym you're using as your ID name. I don't know what program you're running, but isn't there something you click on to access your e-mail on the home screen? If it asks you to log in, it will ask for your "username" and whatever password you've set up. If you haven't set one up, the computer will ask you to enter a new password.

I'm not sure I understand what your other problems are?
PS:
Oh, yeah. If you're online, the message is from Outlook Express, not Microsoft Windows XP. It's Outlook Express that delivers your mail.