Due to Windows 8 being possibly the worst operating system that has ever existed, when Windows 10 was released I decided that I would play with it for a while before taking the plunge and migrating from Windows 7. I purchased a brand new drive for the occasion which would allow me to keep my existing Windows 7 installation safe, just in case.
A few days into using Windows 10 (with all the privacy-shattering junk disabled), I decided that I liked it enough (or in some cases, didn’t dislike it too much) to stick with it, given that Windows 7’s support will cease in the not-too-distant future. So I re-connected my Windows 7 drive in order to migrate some application data. After booting into Windows 10, my former C: drive was mapped with the letter F: and I began copying over the data that I wanted to keep.
A reboot later, I noticed that almost all of the network drives that I had mapped had disappeared from “This PC” – at least, each of the drives with a letter that followed F: in the alphabet, but the ones that proceeded F: were still there. Yes, I have a few network drives.
I discovered that the drives were indeed still mapped, and typing “X:\” (where I keep setup files) into the address bar would reveal the drive and temporarily bring it back to “This PC”, only for it to disappear again once I closed and re-opened the window. Unmapping and re-mapping the drives made no difference and neither did this workaround.
I lived with this quirk whilst copying over the data that I wanted from the drive, then decided to experiment a little to find out exactly what was causing the mapped drives to disappear from view. First I formatted the F: drive so that it was empty, thinking that perhaps Windows didn’t like that there were two Windows installations present. This made no difference. So I opened Disk Management and deleted the 100mb “System Reserved Partition” from the drive as well as the ~250GB partition used for data, then created a new partition from that. Immediately all of my network drives re-appeared!
So it seems that there’s a little bug in Windows 10 whereby connecting a second system drive with a “System Reserved Partition” present seems to break the visibility of network drives in “This PC”, even though they can be used without issue when the drive letter is manually entered into the address bar. If you have network drives that refuse to stay shown under “This PC” therefore, ensure that you don’t have such a drive connected!