Preparing to upgrade to Windows 10

I presently am dual booting Windows 7 32bit and Windows 8.1 64bit. I have downloaded the Windows 10 files and want to update the W8.1 installation only. I intend to remove all drives except the one that has the 8.1 installation before running the update, but was wondering if I should also delete the dual boot, then set it back up after I am sure that all is well with the installation.


Mostly Harmless
Staff member
Hi Bob,

If you remove the drive that contains Windows 7, there's a good chance that your resulting configuration post-update will not include a dual-boot anyway as Windows might just rebuild the BCD with whatever OSes it can access.
If the entry is still there, it'll obviously not work until you reconnect the Windows 7 drive; but it should work once you do.

So long story short, no real need to touch your BCD configuration at all before you update.

Best of luck!


Knows where his towel is.
Staff member
I had the same setup, 7 and 8.1 and also decided to keep the decent OS and let 10 replace 8.1
The only tweak I made before upgrading was to set 8.1 as the default system so that it could do its multiple reboots during setup without any intervention. (It probably would have done so itself, but I was just being cautious)
Everything went fine.
Afterwards I turned off W10 fast boot
and put W7 back as default and am now back using that with W10 sitting unused in reserve.