I'm in the exactly same situation of Pulytr. (small company, switching from Intel to Gigabytes motherboard, want to modify S/N (OEM computer builder))
Two years after, nothings comes up?
My investigation leads me on this web site...
http://businesscenter.ca.gigabyte.com/default.htmIf you clic on "Support" / "Integrator Tool Kit", it ask for username/password. I don't know if this "integrator tool kit" will do the same as Intel Integrator toolkit (ITK). If then, I assume this is for computer's OEM builder (not for modo constructor, Gigabyte in this case)
Anyone (OEM Builders) have ever go thru this?
"To be filled by O.E.M." instead of real serial number is very annoying for computer inventory ;(
Sorry for my poor english