First, try the built-in location reset, even if you think you already did. Open File Explorer, right-click Downloads in the left sidebar, choose Properties, then go to the Location tab. Click Restore Default, then Apply. If it asks whether you want to move files, say No for now. If this works, Downloads should point back to C:\Users\YOUR_USERNAME\Downloads.
If the Location tab is missing or Restore Default is greyed out, then Windows has lost track of the Downloads folder entirely. In that case, manually recreate it. Go to C:\Users\YOUR_USERNAME\ and check whether a Downloads folder exists. If it doesn’t, create one yourself and name it exactly Downloads.
Next, fix the registry entry directly (this is the correct place—many guides point to the wrong key). Press Win + R, type regedit, and go to:
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\User Shell Folders
On the right side, look for a value named {374DE290-123F-4565-9164-39C4925E467B}. That long string is the Downloads folder identifier. Double-click it and set the value to:
%USERPROFILE%\Downloads
Make sure the type is REG_EXPAND_SZ, not REG_SZ. If the entry doesn’t exist at all, create a new Expandable String Value with that exact name and value.
After that, close Registry Editor and restart Windows Explorer (or just reboot). When you open File Explorer again, Downloads should reappear correctly and no longer point into OneDrive.
If OneDrive keeps “helpfully” moving it back, open OneDrive Settings → Sync and backup → Manage backup, and make sure Downloads is turned off there. OneDrive’s backup feature is often the root cause of this problem.
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hth
Marcin