I keep my catalogs and media files on an external usb3 drive, which I need on various occasions to plug into my Mac or my Win7 machine to run LR from either one.
On the Mac, no problems, it sees the unc path of the files, so all the folders showing in Lightroom are OK.
But Windows sets the drive up with a mapping - it was F:, now today became E:, not sure why - and of course then I get questionmarks with all the folders in LR.
When I tried to relocate the folders to remap, weird things happened: some LR folders only showed a few images, but in Explorer you could see all the files were there. Yet I couldn't re-import or synchronize. It would go thru the process and say no images were imported. I ran "find all missing photos" and it's 9000 out of 15000 pics. They're all, there, I can open them from the "All Photos" grid, but have to then re-locate each individual file.
How do I clear up this mess in Windows, I can't always use my Mac. Is there a way to set up the external drive in Windows without a drive mapping?
You can change the drive letter of a drive manually: Change, add, or remove a drive letter - Windows Help
If you set the drive letter back to F: and you still have photos that are missing, let us know.