I'm updating my main but old system to Windows 10 Professional. This is the 4th one I've done and every one has thrown up problems that I've managed to resolve however this one has me puzzled. Because Windows 10 wouldn't upgrade the system I've had to do a fresh install. I can see a disk assigned to drive m:\ in disk management but is not visible in File Explorer. If I change the drive letter to another then the disk is visible. I've tried with 3 drives (2 x USB and i internal) and it's the same with each one. All the drives work fine otherwise. The disk was visible as drive m:\ when running Windows 7 Pro 2 days ago. It's not a major problem but it's nagging at me. Anyone with any idea how to resolve?