1. Open Control Panel
Click start and then type in control panel and press enter.
2. Open System
Click on System.
3. Change Settings
In the section where it says "Domputer Name, domain ..." Click Change Settings.
4. Click Change
Click Change at the bottom of the Computer Name tab. A new window will appear. You can type in a new computer name and then Select domain(Under Member Of" and enter in the domain details, once prompted enter in the username and password.