That has not been my experience. I do not think the OS can write to the BIOS, UEFI or otherwise, because updating a BIOS can be a painful experience if it goes wrong. I would hate to think ms is doing that as they cannot seem to get an update out without issues, never mind writing to my BIOS.Even if you don't create a MS account, they remember your product code. I think it is stored in BIOS or equivalent. (what's that called, UEFI?) I do installs frequently for practice and I almost always set up the systems with only local accounts like Linux and previous versions of Windows have.