Create a NEW account of the name you want. Now log in there and see what happens. Move all your stuff to the new account as you have time.
I bought my wife a pc (used) windows 7. I got it from a guy named "wayne" he had it named "Waynes ****" so I changed the user name but still when somthing saves to documents, my computer ect it saves as "waynes ****" what can I do??????