Product Keys: install from different disk then product key disk

As mentioned, there is no product key stored on the disk. They make a master and then stamp out copies of that, they are all identical. What can get you is if your code is for say Home Premium but the disk is coded for Pro. If the key doesn't match the version on the disk it will be rejected. There is a way around that though, just delete the ei.cfg file to make it a universal disk. Windows 7 Universal Installation Disc - Create
My MSDN ISO's will accept OEM and Retail keys and I believe are identical to Retail DVD's you'd buy off the shelf. Branded custom OEM DVD's are a different matter. I'm not talking recovery media, full install media that you can actually install Windows with. They will have an $OEM$ folder in the sources folder. That is where the OEM-SLP activation files and other OEM branding is. Delete that folder and it becomes a regular disk. As far as I know anyway. Leave it there and if it see's the correct OEM BIOS SLIC table, it will do an OEM_SLP setup. If it doesn't it should then prompt for a product key. That will work but you may end up with side effects. Like say Dell logo's on your Acer laptop etc. You may get incorrect drivers installed too. Better to just nuke the $OEM$ folder if your using it on another brand of PC.

What pbcopter said in reply #2 :)

As long as you use a Home Premium key for Home Premium, a Professional key for Professional etc, and as long as that key has not already been used to activate windows.