There is no such thing as "cannot delete partition", everything created can be deleted as in everything created can be destroyed
Anyway, if it had xp on it, I would not suggest vista, because it might not have the necessary hardware for it.
But it's easy, don't let yourself discouraged. Ask questions here and I'll try to help you or better yet, get a friend that knows what he's doing... this should be done in no time (aprox 30-50 minutes with all basic programs for music and videos).