A motherboard tattoo is a unique identifying code which is embedded in the BIOS of an operating system. The motherboard tattoo contains information about the system, including the motherboard used, and it is individual to the computer it is installed in. By creating a motherboard tattoo, a manufacturer can ensure that only authorized diagnostic and recovery discs are used with its products, as the computer can be programmed to reject unauthorized materials.
Many computer users are totally unaware of the motherboard tattoo, and it rarely becomes an issue. If a computer becomes damaged in some way and a user attempts to use recovery or diagnostic discs designed for another computer, however, an error will be generated. Likewise, discs generated for a computer with a specific motherboard tattoo will not work in other computers, and this can be both frustrating and irritating.
The motherboard tattoo can also become a problem in the event that a motherboard or other components in a computer are replaced. If the computer later requires troubleshooting with support or recovery discs, these discs may fail to work because the tattoo does not match the hardware components. For this reason, people who replace motherboards and other components should be careful about what they are doing, as special software is needed to reprogram the motherboard tattoo.
As a general rule, a motherboard tattoo is only present in built systems manufactured by computer companies which sell packaged computers to consumers. When someone builds a computer independently from individual components, a motherboard tattoo could be custom programmed into the BIOS, but most people choose not to do so.
From the point of view of a manufacturer, the motherboard tattoo preserves the integrity of their product, by encouraging consumers to go to the manufacturer for repairs and services, and for replacement parts. For consumers, the motherboard tattoo can be viewed as a frustrating operating system feature which makes it hard to upgrade the computer or to make changes to its hardware.
If you aren't sure whether your computer has a motherboard tattoo or not, consider the source. If you ordered your computer as a complete system from a manufacturer, chances are that it probably does have a motherboard tattoo. If the system was custom-built for you by a friend or a company which specializes in such things, ask them whether or not a motherboard tattoo has been embedded in the BIOS. It is important to know this before opening a computer up to replace or fix components.