Sellin hard drive, need to delete user

After having a few problems with our computer we are getting a new one, would like to sell the hard drive as Im sure there are people out there that would like to tinker! Before I sell it want to clean it out totally including deleting our user account. The best way I thought to do this was create a new user and then delete the old. The only thing is, one of the problems we had with the computer was it wouldn't create new users. It configures the desktop and then goes to a new screen with a box in the top left hand corner
saying: 'Setting up personalized settings for windows desktop updates.'
And then does nothing, have even left it for quite a few hours in the hope its just one of these things that takes time and it still dosn't change.

So my question is, how can I delete all my information without leaving anything behind, and would manually deleting everything and then changing the username and password be enough?

Thanks heaps, and wish I'd known about this site when we first got Vista, would have saved me from banging my head against a brick wall a few times!!

Welcome
Did you know that when you delete, including accounts, the information is still there. The path is merely blocked so it cannot be accessed. It is not truly delted until the space used several times.
Professionals use zero formatting, you can use eraser
Eraser

Read the information about eraser and you will be so glad that you came to the forum, You know your bank password and stock account etc is on that hard drive.

You can also format, which is great way in edition to using software
http://www.tech-faq.com/how-to-remove-all-personal-files-from-windows.html

To format just use your installation DVD, format will be an option.