Dave has gotten a notice that he will be upgraded to Windows 10 on a certain date unless he cancels it. So he did. Leo says that Microsoft is really pushing for users to upgrade to Windows 10, whether they want it or not, and less savvy computer users may find they've been upgraded without their notice. It's pretty nefarious. Users do need to agree to the EULA to use it, but that's after Microsoft has installed it and if you don't want Windows 10, you'll have to uninstall it.
Dave wants to know how a RAID is controlled by the OS. Leo says that it isn't. A RAID is handled by the computer's BIOS, not the OS. Windows will see the RAID as a drive, and it isn't really controlling it.