What OS's are involved with the dual boot and what OS is set as the first boot OS?

Is it a memory (RAM) issue?

I had a Windows 7 Desktop PC machine years ago throw all sorts of random messages then BSOD, and all at different times during the boot up process.

The machine had 4 Ram modules in it, and I took all of them out, and tried each one individually. With 3 of them the machined booted, but on the 4th one, it would randomly go to the BSOD.

Not saying this is the problem your having, but it maybe something else to check.

Rikkitic:

 

This is also not a Win 10 issue. As stated in my original post, it is Win 7. I am going to upgrade to Win 10 on a UEFI machine, but I need to get these drives to boot first. Once I have the stuff I need, I will reinstall on the Win 10 machine.

 

 

 

That's a shame. The DISM tool isn't on Windows 7. If you just need to get your files off, then you could make a bootable USB drive using Linux Mint, boot it on your sick PC, then you should be able to view all your hard drives and move files and folders to where you want them.

One last thought. Maybe you have a virus infection. Have you tried a USB bootable antivirus scanning tool to scan all the drives?

https://www.digitalcitizen.life/top-free-bootable-antivirus-rescue-discs-windows-pcs

I can access the files. That is no problem. But I need to boot the drive to get the system info I want. I was already pretty sure there was no virus but I ran a complete scan of the drive with Malwarebytes last night just to check and it found nothing. I don't know if RAM is an issue with the dead pc. It is certainly possible. I may go back and check again. I am juggling a lot of things at the moment.

Thanks to everyone by the way for your suggestions. I appreciate the help.

yitz: Try this for an easy, complete solution: https://www.sevenforums.com/tutorials/292068-make-windows-7-bootable-after-motherboard-swap.html

Wow! That really looks like it might do it. I will definitely give it a try. Thanks heaps.

In the meantime, some other things have happened. I'm not sure I can call it progress, because this is without a doubt the most confusing situation I have ever encountered. I haven't got a clue what is going on. I can't make head or tails of it.

Anyway, here goes: The drives in question have Win 7 and Vista on them. This is how I originally set it up several years ago. Vista is there because it was there originally and it has a lot of video tools on it that I don't use any longer but didn't want to lose in case I ever needed one again, but that were not worth the trouble of upgrading and maintaining on a more modern system. So I just kept them where they were. The dual boot has always worked fine and I usually just booted Win 7.

The Win 7 drive I have maintained and kept up to date (except that it is still Win 7). This has been my main system for several years and it meets my needs perfectly. I also have Win 10 on my laptop, but I still prefer Win 7 for regular use.

The computer containing these drives completely died after a series of blue screens. I couldn't get it to respond at all. I tried the drives and back-up copies in two other machines, one legacy, the other with UEFI, but could only get BSOD errors when starting. I tried everything to repair the Win 7 drive, including running all the recovery tools from the Win 7 DVD (same version as the installed one). No faults were found but I still got the BSOD. 

I desperation, I decided to take another look at the dead PC and put the drives back in it. To my surprise, it came to life and began to boot. No BSOD this time, but it did run chkdsk. Then it abruptly died again. I removed a card and replaced the RAM and it started normally and reran chkdsk, which completed with no errors reported. Win 7 seemed normal again but the Vista drive was completely dead. Windows didn't see it at all. I removed it and am going to check it out later, but it is not a priority. At the moment the 'dead' pc seems to be working fine with the Win 7 drive. I am letting it run to see if the BSOD returns.

After the Win 7 drive booted successfully, I tried it again in the legacy pc and again I got the BSOD. For whatever reason, that drive will only work on the one pc. My next project is to try the trick above to get it to work on the UEFI pc since I can't trust the reliability of the other one. However, I have achieved my goal since I can now boot the drive and get the data I need.

But what a hassle getting there. I am too old for this crap.

Thanks again to everybody for helping me out with this. It has really had me scratching my head.

The above worked like a charm! I can't believe it. That is truly miracle software. I wish someone had pointed me there in the beginning. Thanks again, @yitz. I owe you my life.