OEM BIOS Emulation Toolkit For Windows Vista x86 v1.0.

Copy/paste from the Readme:

Microsoft allows large hardware manufacturers (e.g. ASUS, HP, Dell) to ship their products
containing a Windows Vista installation that does NOT require any kind of product activation as
this might be considered an unnecessary inconvenience for the end-user.
Instead these so-called 'Royalty OEMs' are granted the right to embed certain license information
into their hardware products, which can be validated by Windows Vista to make obtaining further
activation information (online or by phone) obsolete.
This mechanism is commonly referred to as 'SLP 2.0' ('system-locked pre-installation 2.0') and
consists of the following three key elements:

• The OEM’s hardware-embedded BIOS ACPI_SLIC information signed by Microsoft.
• A certificate issued by Microsoft that corresponds to the specific ACPI_SLIC information.
  The certificate is an XML file found on the OEM’s installation/recovery media, usually called something like ‘oemname.xrm-ms’.
• A special type of product key that corresponds to the installed edition of Windows Vista.
  This key can usually be obtained from some installation script found on the OEM’s installation/recovery media or directly from a pre-installed OEM system.

If all three elements match Windows Vista's licensing mechansim considers the given
installation a valid system-locked pre-activated copy (that does not require any
additional product activation procedures).

So the basic concept of the tool at hand is to present any given BIOS ACPI_SLIC information to Windows Vista's licensing mechanism by means of a device driver.
In combination with a matching product key and OEM certificate this allows for rendering any system practically indistinguishable from a legit pre-activated system shipped by the respective OEM.

[…]