The 64-bit versions of Windows support running 32-bit Windows applications. This presents a problem because many Windows subcomponents are present in both 32- and 64-bit versions, and information about them (such as program filenames) is stored in the Registry under keys whose names were determined before Microsoft considered the need to distinguish between the two flavors. To manage this, Windows stores information for 32-bit components in an alternate location and feeds the stored information to 32-bit applications when they ask for values from the original location. This is called Registry redirection. The information for 32-bit applications is actually redirected to HKEY_LOCAL_MACHINE\Software\WOW6432Node. When a 32bit application requests information from a redirected key using the original location, it is fed information from below WOW6432Node.
You must close the 64-bit version of the Registry Editor before you can open the 32-bit version, and vice versa, unless you start the second instance of the Registry Editor with the -m command-line argument.
When working with the Registry on a 64-bit system, you need to know to look under WOW6432Node when looking for setup information for 32-bit components.
Alternatively, you can use the 32-bit version of regedit; this presents all information in the standard locations seen by 32-bit applications. When you run regedit from the command line, you get the 64-bit version. However, if you run %systemroot%\syswow64\regedit.exe, you get the 32-bit version and can edit the values seen by 32-bit applications.
So that the 32-bit and 64-bit versions of components and applications can communicate, some settings and values that these components store in the registry are copied to both locations. This is called Registry reflection.
Reflection was used in several sections of the Registry in Windows Vista, but in Windows 7, only two keys are subject to reflection:
For more information on reflection, see Microsoft Knowledge Base article 305097 at http://sup-port.microsoft.com/kb/305097. Also, search msdn.microsoft.com for the article titled "Removal of Windows Registry Reflection."
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