Backup works fine, but backup drives will not boot

I have 3 drives in my computer and I backup drive #1 to drive #2 one week and then drive #1 to drive #3 the next week (clone process).  I upgraded to Windows 10 and everything seemed fine until I tested one of the backup drives to make sure it was bootable.  I have done this befor on Windows 7 with no issues at all.  Now that I am on Windows 10, neither backup drive will boot unless Drive #1 is still in the computer, then it boots, brings up all the icons and then the screen goes black and the computer just sits ther with nothing happening. If I remove all but the backup drive, nothing boots at all.