The DMI check would be the basic one that prevents you from going past the initial screen on a recovery disc. The actual activation of Windows has moved on now. I've not seen a partition check though.

Vista and Windows 7 use special certificates called SLICs which are embedded into the BIOS now. Each manufacturer gets a SLIC for each edition of Windows they bundle. This hasn't stopped people since there seems to be a growing number who modify their BIOS to include one of many OEM Windows SLICs.

nVidia SLI support uses a similar mechanism to enable itself on non nVidia chipsets. If the manufacturer pays the necessary license fee then they include the certificate into the BIOS. Again, people have been busy modifying their BIOS to enable this.