I am running Win7 and Win8.1 in a dual-boot configuration. Gigabyte Z68MA-D2H-B3 motherboard which I'd like to upgrade to UEFI [U1C(UEFI BIOS)]. First drive is SSD (OCZ Agility 3 64Gb) with Win7; Win8.1 is on HDD (Western Digital, 2Tb; partitioned for Win8.1 boot 500Gb, remainder for Win7 data). I plan to replace the OCZ SSD with a Samsung 250Gb SSD (850 EVO).
Once all that is done I would upgrade the Win8.1 to Win10.
What's needed to manage the UEFI upgrade where I have two bootable Windows disks? (Can the existing dual-boot setup be preserved or will it need to be replaced?)
I assume both disks would have to be reformatted. etc.