New PC - how do I transfer my ITunes over?

Hi everyone - Am in a right pickle. I've got a new PC (sooo wished I'd spent the extra £££ and got a MAC, but there you go!) and downloaded ITunes with my me.com address hoping it would magically transfer my Itunes acct. It hasn't. And I think it has created a whole new account as my Apple ID is a different email address! Can someone help me please as I'm just about to delete the new Itunes from my new laptop and try all over again and I fear I might delete the wrong bits...

Many many thanks

Clare