Microsoft Knowledge Base Article 321070 contains the following summary:
This step-by-step article describes how to reverse the changes that are made when you run either the Sysprep
utility (Sysprep.exe) or the Riprep utility (Riprep.exe) on a host computer to prepare it for cloning.
You may want to reverse the changes that Sysprep made to the host computer's registry so that the Mini-Setup
Wizard does not run when you restart the computer. After you reverse the changes, the host computer is returned
to the state it was in before you used Sysprep or Riprep.
You can use the procedure that is described in this article if the Mini-Setup Wizard causes the original computer to stop responding (hang), which prevents Setup from completing. You can also use this procedure to troubleshoot the root cause of the issue that is preventing Sysprep from completing successfully. After you find the cause of the issue, you can run Sysprep or Riprep again.
You may also want to use this procedure if you accidentally run Sysprep or Riprep against a production computer but you do not want to change the Security IDs (SIDs) or any of the configurable options for which Mini-Setup Wizard prompts you to change when you restart the original computer.
If you run Sysprep or Riprep on a source computer, it changes the following registry values:
NOTE : Riprep or Sysprep adds the -mini parameter.
After you restart the computer, Setupcl.exe automatically assigns new SIDs to the computer, and then starts the Mini-Setup Wizard to complete the setup procedure.