Thanks, CountMike. If you read my original post, I had been working with EasyBCD, and it didn't solve my problem either. Even when I entered my setup in EasyBCD, it didn't help. It lost it there, too. Probably because Windows only saw one entry in the Bootloader when it started. So this wasn't fixed until I did a repair of Windows 7. From then on, EasyBCD worked with my setup.
EasyBCD v2.2, older one that worked on W7 doesn't work on 8/8.1 or W10 properly.
My situation yesterday:
Win8.1 on primary boot disk SSD
Win10TP on secondary HDD, both bootable by themselves.
Updated W10 and boot was screwed up royally. 5 entries at boot and only W10 would boot.
EasyBcd was installed on primary disk too. I installed EasyBcd on W10 and set boot order and menu, it was down to two W8.1 and one W10 on the boot menu. I found executable EasyBcd file on SSD with W8.1 and run it while still in W10, set the boot order and everything came out right. Now I can BOOT thru BIOS to either of disks and get exactly same BOOT menu.
This is why I got those screwless removable trays and hard drive power switch installed on my PC. We need to discnonnect all the other working OSes on the same machine before updating Win 10. Or else, boot managers will get screwed up. But you can also manually disconnect them by opening up your case. :) But if it is a minor update (KB updates), no need to disconnect.
Yes, that's nice to have. I usually disconnect other 2 drives while updating second OS but was too lazy this time.
Thanks, CountMike for the tip about EasyBCD. But I do have version 2.2, the latest one. EasyBCD has always worked great for me. I still think it has to do with the bootloader entry for win 7 needing to be repaired.
Great information provided here! I've gotten gun-shy on the dual boot myself. I just switch the hard drives at boot. I think some of the issues I had were due to sync being on and my Microsoft account. Turned sync off on 8.1 and installed 10074 with only a local account. I may try the dual boot again, I've already had to restore 8.1 twice from the system image, one more time wouldn't hurt. At least this way I can evaluate 10 w/o issues, so far I like what I see.
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