Back in the days of Windows 98 and before, Microsoft included a Registry Cleaner, RegClean or regclean.exe along with the Windows operating system, which was discontinued from Windows XP onwards.
Microsoft RegClean analyzed Windows Registry keys that are stored in a common location HKEY_CLASSES_ROOT in the Windows Registry. It found keys that contained erroneous values, and after recording those entries in an UNDO.REG file, it removed them from the Windows Registry.
RegClean was last updated to version 4.1 several years back. It is now obsolete, no longer used as it is not compatible with many products including Office 2007 onwards.
But Microsoft has nevertheless just updated its KB299958 to list the problems you may face if you were to ever use (why would anyone use it now!?) RegClean Utility with these products installed.
When you install a Microsoft Office program whose installation state is Installed on First Use and then double-click a document that is associated with that program, the Office program may not start. Instead, the Open With dialog box appears and the Office program is not listed. This issue occurs because the RegClean utility is not compatible with Office 2007 1nd Office 2010 products. This issue occurs for any Microsoft Windows Installer product on which the program’s installation state is set to Installed on First Use.
RegMaid was another utility that was designed to clean up invalid registry entries that were caused by deleting OLE projects that were created with Visual C++ and Microsoft Foundation Classes (MFC). RegMaid was thus not meant to be used as an end-user cleaner, but more for programmers machines. Windows 9x and Windows NT officially support this utility. It too has been discontinued.
…And then there was OneCare, which included a registry cleaner to help remove invalid or obsolete registry items on your Windows computer. But this too has been discontinued by Microsoft.
Has anyone here used RegClean, RegMaid in the earlier days? Like to share something about them?