To rename a computer
You must be logged on as an administrator or a member of the Administrators group in order to complete this procedure. If your computer is connected to a network, network policy settings may also prevent you from completing this procedure.
Open System in Control Panel.
On the Computer Name tab, click Change.
Under Computer name, type a new name for the computer, and then click OK.
If the computer is a member of a domain, you will be prompted to provide a user name and user password to rename the computer in the domain.
To open System, click Start, click Control Panel, click Performance and Maintenance, and then click System.
A computer joining a Windows domain must use the name created for it by the network administrator, unless you have a user name and password with rights to create computer accounts
If you supplied a valid user name and password for a secure Windows domain, the domain membership will be automatically updated with the new computer name.
If you specify a computer name longer than 15 characters and you want longer names to be recognized by the Active Directory domain, the domain administrator must enable registration of DNS names that are 16 bytes or more.
If you rename your computer or workgroup when it is disconnected from the network, duplicate computer names might result. Check with your network administrator before renaming your computer.