Is it legal to use a Volume Licencing Key (VLK) if all your devices have an OEM licence?
Yes, as long as you have purchased at least one volume licence for the product in question, i.e. if you plan to use a product like MDT, FOG, g4u or R-DriveImage to image your PCs which came with Windows 7 Professional on, you must have at least one Select or Open licence for Windows 7 Professional.
You may NOT use a Windows 7 Professional VLK to activate a machine which has an OEM of Windows 7 Basic or Windows XP (for example).
Reimaging is the copying of software onto multiple devices from one standard image. Reimaging rights are granted to all Microsoft Volume Licensing customers. Under these rights, customers may reimage original equipment manufacturer (OEM) or full packaged product (FPP) licensed copies using media provided under their Volume Licensing agreement.
Volume Licensing customers who have licensed Microsoft software products from an OEM, through a retail source, or under any agreement other than their Microsoft Volume Licensing agreement may use copies made from Microsoft Volume Licensing media. Customers can use these copies from Microsoft media only if they are the same product and version, contain the same components, and are in the same language.
You must purchase at least one license of the Microsoft software that you want to reimage under your Open License authorization number or Open Value, Open Value Subscription agreement number. This purchase is required to obtain the media and necessary Volume Licensing Keys (VLK(s)).