The migration to the new build is complete. However, it took me nearly 10 hours.

One was the Windows Update that took almost 40 minutes (!) on the temp drive. Noticed something was up when Disk Cleanup was running quite slow.

Two was the fact that I was trying to convert BIOS/MBR to EFI/GPT without any notes! This is the issue that took up a LOT of those 10 hours. Oh, and MBR2GPT always failed converting the system drive... That, and I kept screwing up the way Windows booted, lol.

I now have some conversion notes, but there will be no recovery partition for that system, so it will need installation media whenever something goes very wrong (which is extremely rare).