I hope somebody can either explain to me what I'm missing or point me to an explanation.
I have two 256 Gig SSDs on which I'd loaded different operating systems but virtually identical applications. One was Windows 8.1 and one was Windows 7. They were interchangeable -- all I had to do was shut down, remove one SSD and replace it with the other, boot into BIOS, ensure BIOS would boot from the new drive, and off to the races.
In addition to the SSD I have four 3-Tb hard drives in my desktop setup. Either of the OS installations would identify the drives nicely along with their partitions. No problems with the additional hard drives.
Then I decided to upgrade the Win8.1 installation to Win10. After backing up Win8.1 with Acronis True Image, I let Microsoft do its thing and pretty soon I was running Win10 and everything was great. All my applications, well, nearly all, survived the transformation with drivers intact and they're running just as well as before. I've never experienced an upgrade from one OS to another that went so smoothly. And I like Win10, especially now that I have it looking almost like my Win7 installation. It works the same but it truly seems peppier. I'm happy. Or I was...
This morning I decided to see whether a clean installation would work even better than the upgrade -- maybe I wouldn't get those annoying delays sometimes when starting Windows (File) Explorer. Maybe I would stop seeing the occasional long delay when starting an application -- hard drive runs and runs and runs and then all's OK again. Maybe I could make a good thing even better? "But Bill -- you can't activate a clean installation yet." No problem; I'm just playing around, I've backed up my Win7 SSD with Acronis; a clean installation of Win10 will work fine for a few days even; I can see what happens and then put Win7 right back where it belongs on my secondary SSD. And my new Win10 upgrade SSD will work just fine when I put it back in place. Right?
Well, not exactly, and this is where I need somebody to explain where I went wrong.
I disconnected all my HDDs, attached just the Win7 SSD and my optical drive to my Asus P9X79 MB, and started up using the new Win10 64-bit installation DVD I'd created from the ISO I'd downloaded from Microsoft. When I looked at BIOS before the disk booted I saw I could choose to boot with the optical disk as UEFI or not. I chose UEFI as I seemed to recall doing that way back when I set up Win7 and Win8.1. I thought. I also seemed to recall that even though I chose UEFI back then, when everything was installed BIOS no longer made any mention of UEFI. That was something I saw only when I had a UEFI-capable installation disk in the optical drive. I thought. Heck I thought UEFI was a replacement for BIOS but I seemed never to be able to use one over the other -- thus part of my confusion. On with the story:
So I clean-installed Win10 on my old Win7 SSD from which I'd removed all partitions -- all space was unallocated when I started the installation -- and pretty soon I had Win10 running cleanly on my old Win7 SSD.
Things looked so good I decided it was safe to connect all my HDDs. And pretty soon I had all of them working just fine with clean but unactivated Win10. So far so good -- and I think Win10 is running even better now!
But then I powered down, removed the clean-install Win10 SSD and replaced it with the upgrade-install Win10 SSD, and when I rebooted (after setting BIOS to boot from the SSD), apparently, though I cannot be totally sure, upgrade-install Win10 decided to run CHKDSK to "fix" all my hard drives.
I think it must have been Win10's CHKDSK though I can't prove it -- Win10 was tight-lipped about what it was really doing. Anyway, after about 15 minutes of delay, Win10 loaded and it appeared all was well. But all was not well, as I couldn't find all my hard drives in File Explorer.
So I rebooted, and this time it took OVER THREE HOURS for Win10 to load. Before it would do anything it thought it had to fix drive G: and that took forever. But finally it finished and now things are back to normal with all drives and files seemingly in place and working fine.
So what went wrong? I've seen behavior something like this before, but certainly not so extreme. I remember CHKDSK running when I was first installing Win7 some years ago and switching between OSs, and as I recall my solution was to turn off prefetch everywhere I could find it. I hadn't thought about this issue again until yesterday when it cropped up as I went from the update-Win10 SSD back to my old Win7 SSD. Yes, Win7 did run CHKDSK when booting. It thought something had to be wrong with my hard drives. So what am I doing wrong when I expose my HDDs to the different OSs? What do I need to do to one or more of my OSs to make them treat my HDDs the same? Is the problem with prefetch/superfetch? Maybe I've confused things with UEFI? Can anybody explain to me where I'm going wrong or point me to an explanation? I'm certainly not going to put that clean-install Win10 SSD back in the computer until I get this sorted out. Thanks.