Question

If one has installed a new hard drive in their ThinkCentre or ThinkPad or somehow managed to delete everything from the original hard drive, the only way I know of to restore the Windows OS and the factory image is to use the Rescue and Recovery CDs or DVDs.

With nothing else to go by, how do the R&R CDs know that the original image, in particular the Windows OS, is being restored to a legitimate system?