Win 7 preinstalled through downgrade rights in Win 8 Pro 64

[lax20531]

I'm looking to buy a new T430s that has the description "Windows 7 Professional 64 preinstalled through downgrade rights in Windows 8 Pro 64-bit." I'd prefer a machine that has Windows 8 preinstalled, yet the majority of the availability I've found have this description in the TABook.

I'm hoping someone can provide some additional info as to what this means. If the system image has Windows 7, does that mean I'll have to buy an upgrade from Microsoft in order to upgrade this downgraded image to Windows 8? Is there an option within the system image to perform a restore to a Windows 8 image, or will I have to perform the upgrade from scratch as if the image was identical to that on my T420s? I'm trying to ascertain how much effort will be required in order for me to upgrade one of these pre-downgraded machines.

Edited for one additional question: Is there any compatibility issue between Win 7/8 on features like RapidBoot that are installed on Windows 7 and supposedly couldn't be upgraded between different machines (T410/420/430)? If I buy a machine that is preconfigured for Win 7, will I lose the ability to perform a RapidBoot in Windows 8? I'll have a SSD, so this may not even be an issue.

Thanks