If you have the original Ms windows 7 install dvd. it most likely means you have a dirty disk or setup could not read the files off the disk to complete. it could also be down to the device, Dvd rom drive.
Now If you got the Iso file from Ms to burn the image to a blank dvd-r then it is likely you burned the disk at too higher speed causing errors on the disk, so you need to burn the Iso image at a slower speed to avoid errors. It`s a read error.