Anybody can learn stuff, but lessons learned the hard way are the ones that stick with you. Case in point: I’ve got a Windows desktop PC I use as a test machine. Furthermore, I’ve got it set up as a dual-boot environment. On one SSD I’ve got a bootable installation of the Win10 Current Branch release (1607.693). On the other SSD, I’ve got a bootable installation of the Win10 Insider Preview (Build 15031). A recent kerfluffle with installing 15031 on that machine forced me to wipe that second SSD, and perform a clean install. As I did that, I remembered that one should disconnect drives before multi-boot install on a Windows PC. That way, I corrected an earlier flub where my Current Branch drive booted up both Windows versions (because I didn’t disconnect the other SATA drives before performing that install).
Why Disconnect Drives Before Multi-Boot Install?
Apparently, if you add a second OS instance the Windows Installer simply updates boot entries for the Boot Configuration Data (BCD) table for the already-installed OS. Thus, it adds the partition information for the second OS to the boot table on the first OS drive. That’s how it shows up on the boot menu for the PC involved.
But if you disconnect all other drives on a system except your OS target drive, you get a clean setup. Then the new target drive has its own independent BCD table. Also, one boot drive isn’t dependent on another boot drive for the Windows bootloader that brings it to life. Of course, that also means you must rebuild the new BCD to take note of the prior Windows install so can boot it selectively as well.
Working with EasyBCD Instead of BCDEdit
Windows offers a built-in BCDEdit command line utility you can use to manipulate this information, but it’s a bit of a slog to use. Although it costs $30, NeoSmart Technologies’ EasyBCD is a worthwhile and friendlier replacement. After I wiped the second SSD, installed 15031, and got all the way through updates and cleanup, I fired up EasyBCD next and used it to add in data for the previous Windows data (shows up as “Win10 Current Branch” in screencap):
Entry #2 is for the old OS, and Reflect makes it easy to add a repair partition for image recovery.
As an added bonus, Macrium Reflect offers a facility to drop a recovery partition onto a boot drive. This lets you boot into that partition from the boot menu. Then you can run Reflect on its own to restore partitions from an image backup. A handy way to recover from serious Windows issues, but only if you have a current backup handy!