America On(cough)line question...

I don't use AOL but my girlfriend does. She has a computer in her room that came from her dad's office, (this could get confusing). He has an AOL account for his computer at his office, (which is now the computer she has in her room). Anyhow, she didn't know how to add her screen name from the account at home to this other computer, (not needing her dad's existing work screen name). So what she did was used sign on as guest and just did it that way, well, now they got a new home pc, and she uses their old home pc, come to find out the old pc has everyone's screen name on it except hers... does this have something to do with her signing on as a guest numerous times? Will uninstall and reinstall fix this problem or does it get the dialog box screen names thingy from AOL? Any input would be appreciated.

Thanks.
Sorry if that got wierd.