I recently complete my homebuild (specs below) and while it booted up fine, my copy of Windows 7 doesn't seem to be working. It never seems to complete its installation without crashing partway through. I often get notices that say that the windows version is corrupted.
I've tried installing it multiple times, but I've had no success with any of them. I've also tried cleaning the disk in an attempt to get the data from it better, but that doesn't seem to work either.
If it helps:
I5 3570K @ stock
Z77 Extreme 4
Caviar Black 1TB
Sony 24X DVD +/- drive.
I don't see anything on that link that says, "Download Now". Maybe that's an option during checkout (not in the UK, so I can't go there). All I'm saying is that I've never heard of being able to download Microsoft Windows from Amazon (purchased and delivered, sure, but not downloaded).
Also, when you do purchase Microsoft Windows 7, it comes on a DVD, not a CD. Windows 7 does not fit onto a CD. So if you are downloading the ISO and trying to burn it to a CD, the burn is probably failing and that would cause the OS install to fail as well.