Problems downloading apps on ipod touch?

My boyfriend got an iphone today, so he's given me his ipod touch (1st gen). I have registered the ipod with my own apple id and pword, but when I come to download apps it says either an error occurred in itunes or, if I try to download via the touch itself, that authorization failed. I'm uming it won't let me because it doesn't recognize my id and pword, so how can I download apps, either through itunes or the touch?