Nonhierarchical File Manager (developed in Visual Basic 6 between 2003 and 2007)
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Compiles in Visual Basic 6, Service Pack 6, Windows XP/2000/2003/Vista/7
It has continued to work on systems up to and including earlier versions of Windows 10 with some degrading of the UI. However, in the current version of Windows 10, it will not run because it's not finding a required registry setting.
Future work: I have none planned. Would require a VB6 IDE to run on a Windows 10 machine to debug the registry issue, which may be in the third-party code of cRegistry.cls. Would be delighted if someone took that on.