OneDrive won't allow installation on fixed D: drive

I hit the same refusal on 8 November and found the cause. Posting it for anyone else stuck here.

OneDrive asks Windows what kind of drive a location is on, and accepts only a fixed or removable disk. On my PC a Windows folder setting, "Local Downloads" ({7D83EE9B-2244-4E70-B1F5-5393042AF1E4}), pointed at the root of D:, and D:\ held a hidden desktop.ini for it. With that, Windows reports D:\ as a folder instead of a fixed disk, and OneDrive refuses every location on the drive with "Your OneDrive folder can't be created in the location you selected". C: was accepted throughout.

To check, run this in PowerShell (not as administrator). Any result is a Windows folder pointing at the root of a drive:

(Get-ItemProperty 'HKCU:\Software\Microsoft\Windows\CurrentVersion\Explorer\User Shell Folders').PSObject.Properties | Where-Object { "$($_.Value)" -match '^[A-Z]:\\?$' } | Select-Object Name, Value

To fix:

1. Point that entry at a subfolder. For example, using the name your check returned:

Set-ItemProperty 'HKCU:\Software\Microsoft\Windows\CurrentVersion\Explorer\User Shell Folders' -Name '{7D83EE9B-2244-4E70-B1F5-5393042AF1E4}' -Value 'D:\Downloads' -Type ExpandString

If you change it through the Downloads folder's Properties > Location instead, click No when Windows offers to move the files: the old location is the whole drive.

2. Delete the hidden desktop.ini at the root of the drive.

3. Sign out and back in, then set up OneDrive and pick the drive. Mine was accepted at once, and OneDrive is matching the existing 649 GB against the cloud without making duplicates.

The desktop.ini dated from January and OneDrive accepted the drive until 8 November, so something changed on Microsoft's side. Microsoft: OneDrive should either accept these drives again or say why it refuses them. A message naming the cause would have saved me two working days.