I know this is a Linux forum but this problem does have to do with Linux. Please hear me out.

This all started when I got an Alienware 15 R3 last year. Here is what I have done over the course of a year in order:

1. I took the HDD out of the Alienware and replaced it with a 1TB SATA SSD. I never once turned on MS Windows 10. I wrote "AW" on the HDD with a marker and put it in a drawer—I had plans for it right from the start.

2. I installed Linux Mint Cinnamon.

3. I bought an M.2 SATA 3 SSD last night and put it in the machine (there are slots for a total of four SSDs). I installed Linux Mint on it.

4. I cloned the original HDD (that came with the Alienware) to the 1TB SATA SSD I mentioned above.

5. I put the cloned 1TB SATA SSD into the proper slot and turned the machine on.

6. I was unable boot up into Windows but I can boot up into Linux just fine.

I thought it had something to do with UEFI vs. Legacy and/or secure boot vs. unsecured but I changed all of that stuff in the BIOS in every way imaginable to no avail.

I thought what would happen would be that I'd turn the machine on, go to Grub, and see an option for logging onto either LM19 or W10. I don't see that option nor do I see any other way to log onto Windows. Of course, I can see the other hard drive from Linux and everything looks good. It looks like a typical Windows C or D drive (or whatever it is).

Ordinarily, I wouldn't worry about it this much, but I need W10 for school and work and I use Linux for everything else.

If Grub isn't showing your Windows os it's most likely because Grub doesn't know about it.

Open the terminal and run:

Reboot and you should see Windows in your Grub menu:-

And if that doesn't work, go here, do as it says and post the output using [code] tags so we can read it.

Unless you have an EFI install with a Boot from EFI file option in the BIOS, I don't see how you could possibly expect to boot windows after the steps you took.

What we don't know is whether your windows 10 was an EFI install (highly likely) and if it was and you removed that drive before installing Mint, did you then install Mint EFI or Legacy? If EFI, you would have had to create an EFI partition on the Mint drive which obviously would have no information on the windows system which was not attached during the Mint install. So the suggestion to update grub would be the first likely step and running boot repair and posting the output should provide enough information for some one to suggest a solution.
The script should tell if both systems are EFI, if Mint is not you won't be able to boot an EFI windows.

The problem was the cloned SSD was damaged. I bought a new SSD, installed W10, and it works like a champ with the exception of a minor annoyance about which I have started a new thread here.

Please mark your thread Solved:-