Volume licensing

In software licensing, a volume license key (VLK) denotes the product key used when installing software licensed in bulk, which allows a single product key to be used for multiple installations.

This form of licensing typically applies for business, government and educational institutions, with prices for volume licensing varying depending on the type, quantity and applicable subscription-term. For example, Microsoft software available through volume-licensing programs includes Windows XP, Windows Vista, Windows 7 Enterprise, Windows 8 Enterprise, Windows Server 2008, Microsoft Office 2007 and many others.

Volume licenses are not always transferable; however, some types of Microsoft volume-license can be transferred provided a formal transfer process is completed, which enables Microsoft to register the new owner. A very small number of software vendors specialize in brokering such transfers in order to allow the selling of volume licenses and keys. The most notable of these, Discount-Licensing, pioneered the sale of Microsoft volume licenses in this way.

Starting with Windows Vista, Microsoft replaced VLKs with Multiple Activation Keys (MAK) and Key Management Server (KMS) keys. Hosts activated via a KMS have to report back to that key server once every 180 days.

Microsoft's licensing for volume license products requires that volume licensing be an additional cost or license, applied over the top of an existing qualifying Microsoft product license. Windows license data is stored in the computer's BIOS in an area referred to as the "ACPI_SLIC", so that KMS can detect the use of previous Microsoft products even with the storage device removed or erased.

KMS licensing of a client device will be refused if licensing entries for a prior qualifying Windows license either do not exist or are corrupted in the ACPI_SLIC table. KMS client refusal can also occur if a properly qualifying Windows license was previously installed but the motherboard manufacturer did not correctly enable ACPI_SLIC in the BIOS.

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