Customers installed Win8 and got the following error:
“We are not sure what happened, but couldn't finish installing windows 8 Consumer Preview. We've set your PC back to the way it was right before you started.”
Running setup from the root of the media within an existing Windows installation assumes that you want to perform a clean installation with data migration.
Running setup from the sources folder gives more of a Windows 7-like experience where it asks you what you want to do.