To rename a user account

To open Computer Management, click Start, and then click Control Panel. Click Performance and Maintenance, click Administrative Tools, and then double-click Computer Management. 

Because it retains its security identifier (SID), a renamed user account retains all its other properties, such as its description, password, group memberships, user environment profile, account information, and any assigned permissions and rights.

A user name cannot be identical to any other user or group name of the computer being administered. It can contain up to 20 uppercase or lowercase characters except the following:

" / \ [ ] : ; | = , + * ? < >

A user name cannot consist solely of periods (.) or spaces.

Local Users and Groups overview

Change the password for a user

Create a new user account

Delete a user account

Disable or activate a user account

Modify a user account

Rename a user account