We (Kanzen Solutions and I) ran into an issue with a new laptop the other day. When trying to install Windows 8 Pro (OEM) onto a laptop which used OEM Activation, the Windows 8 Pro installer pulled the key from the BIOS and once installed was activated as Windows 8 and not Windows 8 Pro.
To get around this issue, you need to create a text file called “PID.TXT” which need to be put into the router of the Sources folder. To this you will need to created a bootable Windows 8 Pro USB Key, and create the “PID.TXT” onto the key within the Sources folder.
The PID file is formatted like so:
Where the value is the Product Key for your version of windows you are installing.
UPDATE: You can extract the PID from the BIOS using a tool, located here.