What all do you want deleted? For pictures, music, docs click on the start bubble, go to computer>>Local Disk (C:)>>Users>>Your name.
In that folder you will find all of your data that's stored in your media folders. Delete the data that's inside the folders. Not the actual folders themselves.
The easiest way to do it is to go to control panel. Make up another account. (name it something like default, or admin.) Make sure that, that account has admin rights. Log into that account and delete your other one. (The one your using.) Then go to computer>>Local Disk (C:)>>Users>>and make sure that all the data folders for your old account are deleted.
Let me know if this helps.