Are you looking to via the registry, or are you troubleshooting a display error in a specific app?
On modern Windows versions (XP and later), MS Shell Dlg 2 almost always maps to Tahoma . MS Shell Dlg vs. MS Shell Dlg 2 ms shell dlg 2
On older systems (Windows 2000), MS Shell Dlg mapped to MS Sans Serif (bitmap font), while MS Shell Dlg 2 gave better Unicode support via Tahoma. Are you looking to via the registry, or
Understanding MS Shell Dlg 2: The Invisible Architect of Windows UI ms shell dlg 2