Users.....

All of the sudden, I lost almost everything on my desktop all of my files were gone, software, email. It seems as though my computer created a new user Administrator.Crawford?? (my last name). All of my files and such are in my administator folder when i go to C drive , documents and settings, administrator. I seem to be logged in as administrator but what I have access to is the administrator.crawford files?
I can i switch this back to the way it was before?

What I have done for now is copied everything from the Administrator to the Administrator.crawford. Everything is back but my harddrive is twice as full. Things are running very slowly. Also everytime I try to open my external hardrive my computer freezer and I have to control alt delete to get rid of it before I can do anything else.

Anyone know what happened and how I can repair this?