Have you received that notice from Microsoft: "Windows 7 has reached its End-of-Life... " or something similar?
That prompted me to reluctantly upgrade my HP Elite desktop from Windows 7 to Windows 10.
You may find my experience amusing.
While we're admonished to "Please Back up ALL of your files before proceeding.', not only do I do just that, using a program like Acronis True Image, but I also do one other thing: I buy a replacement HDD or SDD, and clone the original mass storage device before upgrading.
In other words, I clone my HDD, then upgrade the cloned disk, saving the pristine original as the ultimate backup.
I had previously upgraded my computer from a 1Tb HDD (Toshiba) to a 1Tb SDD (SanDisk Plus). Using my BYTECC cloning machine, the process was easy, no problems. Went smooth as glass.
Then when I went to use my cloning machine to clone that 1 Tb SanDisk Plus SDD to another 1Tb HDD, I got the error message, "Source is larger than Target."
Unfazed, I tried a pristine-out-of-the-box 1Tb WD drive. Got the same error message.
Concerned that my duplicator was on the fritz, I bought another SanDisk Plus 1Tb and inserted it in my duplicator.
Alas, got the same error message.
Bummer.
So I went back in my HP Elite archives, found a previously cloned HDD Win 7 disk for my P Elite from last April and successfully cloned it onto that fresh SanDisk.
The cloned disk installed and worked without any problems.
The upgrade from Win 7 to Win 10 was accomplished successfully.
My HP Elite desktop is now at Win 10 and all's well with the world!
But now, I have an older version of my desktop.
Well, perhaps that's not a problem: I have a secure storage of all installed programs, and also all of my work: I use an external WD MyCloud storage device on my LAN. Any missing applications, I can just re-install.
Theoretically, the 'original' HP Elite SDD only has copies of downloaded stuff (in its "Download file"), and nothing of any real consequence on the desktop or in local memory.
But there's still that niggling fear that somehow, somewhere, there's something on that original SDD that I just might need.
What to do?
I have a KingWin EZ-Connect device that connects a SATA disk to my computer's USB port.
Perhaps that could be used to look at and then copy over files and such that are on that original SDD Win 7 installation to the HP Elite's current Win 10.
Hooking up the SanDisk SDD to the EZ-Connect, and then hooking the EZ-Connect to the computer,!Viola! I can see all of the files on the SanDisk!
Then it was an easy thing to search and poke and prod to find whatever I wanted to transfer to the new installation!