This has been around for a while but I figured I would repost it 🙂 I’m lame like that. Go through your Windows install like you normally would but when prompted for a key just continue, don’t enter one.
Once, you have booted into Windows, open regedit and goto HKLM/Software/Microsoft/Windows/CurrenVersion/Setup/OOBE/ and change MediaBootInstall from 0 to 1. Open a CMD prompt as admin and type SLMGR /REARM; reboot and enter your key. Profit!