Earlier quoted context omitted.
> Are you referring to all flavors(Home Basic/Home Premium/Pro/Ultimate) from one disk? Installing retail/OEM from one disk has never been the case in my experience No, Home/Pro/Ultimate are separate disks -- but OEM/Retail are exactly the same thing. You have to phone in your activation however, since OEM keys usually do not automatically activate over the internet. Vista and up, there is no such thing as an OEM ISO…
To clarify, I was not speaking of recovery/restore, just clean installs of Windows sans vendor bloat... & h/w drivers. And... you appear to be absolutely correct. "Vista and up, there is no such thing as an OEM ISO image. XP had that and it was a great pain for support..." I was not aware OEM & RETAIL installation media were merged, cannot locate any search results verifying this, but I cannot find any recent issues…
Typically the "OEM" purchase of the ISO Disk comes in just a plain white envelope (with COA sticker somewhere on it) and "no official microsoft support" since it's intended for "systems builders" who microsoft expects to have their own support for consumers. A lot of people who build their own rigs choose this option because the "OEM" package is usually $10-$30 cheaper. The "Retail" packaging just comes with the fancy case with color inserts, etc... and "official microsft support".
If you are building your own rig, you're probably unlikely to call Microsoft for anything. If you are some company's internal-IT, you're unlikely to call Microsoft for anything.... Heck, if you are installing your own Windows installation, you're unlikely to call Microsoft for anything... So i just always buy the "OEM" packaging when I need a new license.
So the difference there is really just the packaging the ISO/Disk comes in and whether or not it has "official" support by Microsoft. Otherwise the ISO image on the disk is identical. :)