|Well, my BIOS is by American Megatrends, and I discovered that they have a set of utilities that includes one called AMIDEDOS. It is intended for manufacturers to be able to change text strings stored in BIOS for things like the Manufacturer, Product Name, Version, Serial Number, UUID, SKU Number, Family, etc., which is what I needed to do. It is not intended for consumer use, but it is out there, and I was able to get it.|
When I ran the AMIDEDOS "DMIEdit.exe" program (right-clicked and ran as administrator right from Windows 10) and clicked on "System Information" in the list, I saw "Product Name | STRING | INVALID" and "Serial Number | STRING | INVALID". The other fields seemed to have valid entries. I double-clicked on the invalid fields and changed them to "H535" and my computer's serial number, respectively, and then clicked on "Update ALL" at the top.
Much to my surprise, it reported that it had successfully saved the new information. And, perhaps even more astonishing was the fact that, when I rebooted, the double-beep and warning about invalid machine type and serial number had disappeared. In addition, the BIOS showed the new values I had entered, and the "Manufacturing Boot Sequence" option (which I understand can be much slower than a normal boot) had disappeared.
Again, I am a bit astonished at how simple it was to actually fix the problem once I had the correct piece of software, which neither Lenovo nor American Megatrends apparently provides to owners, and it took hours and hours of research and searching to figure it out. Use this information at your own risk, though, as messing with BIOS apparently can lead to problems that are not easily fixed. That said, the changing of these text strings seems relatively safe.
I will mention that I also ended up changing the boot method from "LEGACY" to "UEFI" in the BIOS after noticing that selection.
message edited by splinke