Exchange 2000 installation

Is there any way to reverse or undo an incorrect forsestprep when preparing to install Exchange 2000? During a previous installation attempt a co-worker chose to add this 2000 server to an existing 5.5 organization and that was not the plan, plus the 5.5 box was on an NT 4.0 box in another domain! This install needs to be a new Exchange install. Rerunning forestprep does not offer to change that option.