Windows DVDs are all alike, at least the consumer editions are. All that's different is the license key included in the packaging. In fact, the Windows 7 DVD includes all versions but which one is actually installed is based on the license key. I doubt that Windows 8 is any different seeing as you can download the complete installer and burn it to a DVD or flash drive yourself for installation. When you make the purchase at the Microsoft web site, you get a license key that's unique to your purchase, but the media is all the same. If you have to reinstall to the same hardware, the same license key should work. If not, a call to MS will sort it out, as you just did.