renaming user name

Sounds like you don't have Administrator rights, talk to your Administrator.

If you do have Administrator rights, then you can change Registered User in "Regedit" for the program you are talking about.

If you are joined to a DOMAIN you need to be added to the computer as an Administrator in the DOMAIN, not just on the computer.

clear as mud, right?

If you rename a user, it doesn't rename the documents and settings folder because this is your profile folder. It is set in the user profile in the reg.

The easiest way to fix this is to do the following.

Rename the current user back to the old name.
Create a new username with the new name.

Login to the pc with the new name and log back off. (This will setup a profile folder)

Login as an admin (Cannot be the new name) and right click on my computer and go to properties.

Goto the advanced tab and select user profiles.

Select the old user and select "Copy to" and copy it to the new user folder.

There you go.