I just cleaned up 1.2 GB of orphaned cached Windows Installer data files from my C drive. These files are stored in C:\WINDOWS\Installer, and have registry keys that are attached to them. Not all C:\WINDOWS\Installer are to be removed, but sometimes when a windows installer fails, there are orphaned files that are left and a new instant of the same installer created a new folder instead of reuse/cleanup of the old files.
The only method that I currently know that safely removes the orphaned files are using "MSIZAP G" (G is a switch that needs to be passed to the command prompt command). msizap.exe is part of Windows Installer Clean Up utility that could be obtained from Microsoft http://support.microsoft.com/kb/290301.
** I WOULD NOT RECOMAND USING WINDOWS INSTALLER CLEAN UP GUI ** since most users might end up removing windows installers that would be necessary for future maintenance of the applications, but do recommend using the msizap.exe with the G switch to remove the orphaned installers. Note that the GUI does not have an option for removing the orphaned files (or at least I didn't find it).
So, here is my suggestion, can this functionality get put functionality in CCleaner by any chance to prevent having to install the Microsoft package which could also remove useful stuff?