Hidden files in mobile?? Please reassure me.

[ChocFudgeCake]

I want to sell my Nokia N82. I had taken many pictures and recorded clips of me and my family. I have now deleted them and all the rest of private info I had stored there (contact numbers, etc.). But I worry that somehow something might have been retained by the phone/memory card (like a computer hidden file). Is that possible? Am I paranoid ?
Thanks!

mine had a files section that had back ups of all the media on it

i had to just go in to it and delete them

There should be a factory reset option that will delete all user data.