I have two HDDs, both of which are capable of booting Linux. Linux 'sane' doesn't support my old scanner, so I thought I'd have to buy a new one. (It won't work in a VM because Linux can't see the scanner -- odd-ball USB handshaking, apparently.) Then it hit me that I could dual-boot one of my HDDs, load Windows on it, and be able to run my scanner. Cheaper than shelling out for a new one.
Here's the procedure I used:
- Open the PC and disconnect Drive 0 -- /dev/sda/. This will ensure that Windows will not overwrite your good grub loader.
- Boot into BIOS setup, and adjust the boot order so that the HDD boots as Drive0 -- /dev/sda/. Then save the settings and reboot, selecting 'Boot Options' at startup.
- Select the Windows distribution medium. Load Windows as usual (note: If you want to dual-boot the HDD now containing Windows, search DuckDuckGo for 'rebuild grub after installing windows'.)
- Shut down, reconnect the former HDD
- Boot into BIOS settings; adjust boot order.
- Reboot. The old grub menu should appear; boot Linux normally.
- In a terminal, run sudo update-grub. OR use grub-customizer to scan for the installed OSs and create a new boot menu.
--Sadhu!