"OA" is synonomous with "OEM" (preactivated) and the product key is for the version (x86 or x64) originally installed.
Type 2 OEM SLP (original equipment manufacturer system-locked pre-installation) license product keys are architecture specific. It makes no difference whether or not the computer is a laptop, netbook, all-in-one, desktop, or rattrap. It is the source of the software installation, not its target that matters. Royalty manufacturers like HP, Dell, Sony, etc. are licensed to use the SLP technology. Type 2 licenses require a valid SLIC (System Licensed Internal Code) in the BIOS on the motherboard. Type 2 licenses cannot be valid on a system that does not have the correct code in the BIOS. If the code in the BIOS becomes corrupted in some way the user must convert the license to Type 8 OEM COA by entering the COA product key to reactivate.
Type 8 license does not read the SLIC table. Non-royalty manufacturers and fabricators (custom builders) use Type 3 System Builder licenses. These are custom builders, consultants, Microsoft Authorized Refurbishers (minimum of 5,000 units), and Microsoft Registered Refurbishers (less than 5,000 units).
Type 5 Retail licenses are used in any transferable license whether sold in a store or through a program subscription such as MSDN, TechNet, BizSpark, etc. The term "retail" does not mean "boxed copy" and it does not necessarily mean re-saleable. It means transferable from one computer to another. Whether or not a license is re-saleable depends on the source of the license. Subscription licenses are always Not-for-Resale.
Type 1 (KMS) and 6 (MAK) licenses are volume licenses (VLK) and are Not-for-Resale licenses.
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