If it's a CD, it's a fake (or a Repair Disk or just W7 Service Pack 1 Update maybe).
If it's a DVD, maybe it's old or damaged or dirty.
Do you have a working machine to see what's on it?
It should look like this and the DVD shouldn't scrabble around trying to be read (ie damage or dirt or old disk or drive)
click here so, see if you can use Imgburn to make a boot copy iso of the DVD, then burn to new blank DVD.
(right click iso for burn options)