I had someone email my girlfriend some bad stuyff about her and I; they used a random hotmail email address. Anyway to get their password or figure out who it is?
Probably not. That's the annoying thing about web-based email, anyone can get one and most information can be easily falsified.
I'd just try to forget about it and try to not let it bother you. Some people are just jerks.
all you can do is report it to hotmail if it was threatening or abusive.