I thought it would be good to post this exchange on OEM Licensing as we have made some changes to the rules for our partners and also its a very common question that we get through the call centres, I have tried to give the complete picture, licensing and technology as they are so synergised these days its good to see the full story -
Let me start with what you can do with a Windows OEM License:
• You can work with an OEM to create an Custom Factory Image (CFI): the OEM can create an Image from their OEM toolkit and then use their Software Factory Integration service to install onto all your PCs at their factory prior to delivery. This type of reimaging service is available on most OEM business PCs and/or royalty OEMs – e.g. PCs installed with Windows 7 Professional.
• This can be done without any need for a Volume License for Windows.
If you also have a Volume License, there is more flexibility:
• The Volume License for Windows is an Upgrade License – for use on top of the OEM License (usually Windows Professional pre-installed).
• With a VL Windows License you can customize the image yourself or ask the OEM to customize to your specification. The OEM still supplies you with a PC that has the underlying OEM License attached to the PC (this is shown by the “Certificate of Authenticity” (COA) label on the back of a desktop PC or bottom of a laptop.
• Customers can take advantage of customizing Windows Enterprise Edition if they have Software Assurance – which offers more features than Windows Professional (such as disk drive encryption – BitLocker).
• Reimaging rights are granted to all Microsoft Volume Licensing (VL) customers as part of the license agreement(s), customers may reimage OEM Operating systems by using the media provided under their VL agreement, such as EA or Select Plus/Select.
You can reimage an OEM Operating system with VL bits as long as you meet the criteria set out in the brief attached – posted – HERE
Note that there are no reimaging rights for OEM Office unless there is Software Assurance on the PC.
In addition you can find good Windows product licensing information on this section of Microsoft.com/licensing