Turning off Ads in Windows 10 File Explorer
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1. Load regedit.exe and confirm the UAC prompt.
2. Navigate to: 
     HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
3. Locate the ShowSyncProviderNotifications on the right-side.
4. Double-click on it to change its value.
5. If you set its value to 0, the feature is turned off. If you 
   set it to 1, the feature is turned on.

The preference should exist, but if it does not, you may create it. 
1. Right-click on the Advanced value on the left-side.
2. select New > Dword (32-bit) Value. Name it 
     ShowSyncProviderNotifications
3. Set its value either to 0 (off) or 1 (on).