Just got this off google:
You can use the System Preparation tool to perform the following tasks in a manner that is supported by Microsoft:
• Prepare Windows for duplication from one computer to another computer.
• Change security identifiers (SIDs) and other system and configuration settings to make them unique.
• Configure user-specific information to be customized by the end-user when Windows starts the first time.
• Create images of operating systems.
• Automate the Windows mini-Setup program.
• Perform auditing tasks.