setting up users

How can i change the name of the user folders already on my drive? I set up a new admin account and changed the name and password for my user account (my old one but with admin unchecked). But in the user account dialog box i wasn't able to change the short name. And on the drive the folder has its old name. Hope this is clear.

What i am trying to do is use the old name and password for the admin account and use a new name for my personal account.

Also can i simply drag a lot of document files to my users folder and have them hidden from other accounts? I had peviously dragged a lot of folders from my old computer's drives to my new hard disc. They were never put into one user account or another. Thus they are visible to all accounts.