Registry Healer should be installed under every operating system (OS) where user wants to check the registry.
Since Registry Healer searches disks for registry corrections, it is important to select drives or even folders where to search.
If your machine has several Windows® operating systems installed and different system's "Windows" or "Program Files" folders are visible for currently booted system then there're many system files with the same name in different folders. Registry Healer will find all the matched files and may suggest a file correction of not currently loaded Windows installation.
Usually we suggest to exclude from the correction scan "Windows", "Program Files", "Documents and Settings" folders of other installed systems. Not doing so may replace local system file references (such as C:\Windows\some_file.dll) with references to a parallel system (E:\WinNT\some_file.dll). Different Windows® versions have many files with the same names but different versions.