Please note that all Intel® products have unique Serial codes that help us identify the motherboard so I regret to say it is not possible to replace neither the serial number nor the AA number on Intel® motherboards.
What Kevin has said is absolutely correct, but this is not the whole story. While the string fields related to the board itself (i.e. Manufacturer, Product, Version and Serial Number) are locked, the BIOS' SMBIOS implementation provides support for the storage (and modification!) of string fields for the chassis (i.e. Manufacturer, Type, Version, Serial Number and Asset Tag Number) and for the overall system (i.e. Manufacturer, Product, Version and Serial Number). The tool that you need to modify these fields is called Intel® Integrator Toolkit (this is download link). It is possible to use this tool to set the strings for a single system or to produce a BIOS update image that can be used to set the strings for multiple systems. See Intel® Integrator Toolkit Technical Support for additional documentation explaining how to accomplish this.
You are the man N.Scott. Thank you!
Thank you Kevin also.