Technically, you should be using the registry, if you want to be truly Windows.
I hate the registry, and it's one of the dumbest ideas to come along in a very long time from Micro$oft.
That being said, you can determine the current logged in user from the environment ($USERNAME). Under NT, I would place it in "$SYSTEMROOT\Profiles\$USERNAME\Application Data\YourAppName". I don't know about Windows 95/98, but I think they have something similiar.
--Chris
e-mail jcwren