It's too late for the machine I was working on, but for future reference, is there any way to make the machine boot from the factory recovery partition on a GPT drive? DiskPart won't make such a partition Active, so I guess it's down to the BCD?
"active" is a flag in the MBR partition table on a HDD formatted that way.
On a GPT formatted drive UEFI looks for the hidden EFI System partition to find bootmgr and the BCD at boot. There is no active flag.
If you have an installation disc for the OS, you can boot that and have it do "startup repair" to recreate the boot files.
Thanks for your reply. I did run the bootrec commands in WinRE to recreate the BCD. I don't recall whether I then pursued trying a Reset or not. I suppose that would have been the thing to do, and that it is possible from the RE.