Help with address book

I bought my iMac from a friend. Therefore I have all his old addresses in my address book. I have been unable to delete these. Please can someone talk me through the delete addresses procedure. A million thanks if someone can help. I'm desperate!!

What happens when you try to delete them?

Address books

I hope this is answering the thread about address books, I'm finding this difficult to access. When I try to delete the addresses, nothing happens, I've tried File, Edit, pressing the delete button, you name it I've done it - nothing happens!!

So, if you highlight a contact, go to edit in the menu bar, and select delete card, nothing happens?

I am suspecting a permissions problem.

Personally, I would erase the HD, reinstall OS X, and not have anything of your friends' on the iMac.

Otherwise, at least create a new admin account and delete his/her account.