>>1. If the SSD has a PCIe/NVMe interface then in order for it to be bootable it requires boot drivers to be installed. Windows 7 doesn't have them by default, I don't know about 10 or 8.1. If you're doing a fresh installation of Windows typically you press F6 when prompted by Setup and load the drivers then. A straight clone of a SATA magnetic HD to such an SSD typically won't be bootable (even if the machine BIOS is set to boot from that device). A workaround that works some of the time is to install the SSD while still running off the HD, then get Windows to detect the new hardware and install the drivers in the HD. Then when it's cloned the drivers are already installed
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>That's among the reasons I switched to Ubuntu. It recognized the SSD immediately, formatted it as I wanted, didn't even think to ask for a driver.

Well, current Ubuntu is a lot newer than latest W7 ;)

>And I have half of that disk to a VM file to run W7. W7 now boots much faster than when it had its own SSD (which died after two years, BTW - an Intel).

I think at one point you said you were using VirtualBox on Ubuntu to run your VMs (?) How has that worked for you?

A number of years ago I got the impression it wasn't a good experience (might have been the 3.x days) but Oracle has been putting some effort into it lately with the latest 4.x and 5.x branches. I've only used it on Windows, it's been pretty good.