How to Rename User Accounts on a Windows 7 Home Network
Open the Windows Control Panel, and then click User Accounts and Family Safety.
The User Accounts and Family Safety window appears.
Click User Accounts.
The User Accounts window appears.
Under Make Changes to Your User Account, click Change Your Account Name.
The Change Your Name window appears.
Type in your new account name and click Change Name.
Your new user account name will now appear on the Welcome screen and on the Windows Start menu.