Cannot download anything

I am about to go crazy. I am not very computer literate and I bought one for my husbands business so that I could keep up with finances. I only know the basics. My daughter got on it and put herself in as administrator with a password. But she doesn't remember what the password was and everytime I try to download something it wants the administrative password. I have tried going in and putting me as the administrator and overriding her but I can't without her password. I have also tried to run stuff as administrator and it still wants her password. I am feeling lost and about to pull my hair out.

I have the Vista Program on my computer it is a dell and that is about all I know about it and that I bought it this year.

Please tell me that you know something or some way to delete this or get by it.