Running 32-bit and 64-bit Snap-ins in 64-bit Windows

Microsoft 64-bit operating systems can run both 32-bit MMC (MMC32) and 64-bit MMC (MMC64). MMC64 cannot run 32-bit snap-ins, and MMC32 cannot run 64-bit snap-ins. This topic describes how to determine and control which version of MMC is executed in 64-bit Windows.

MMC can be executed with command-line parameters, such as a console file name. Additionally, the following command-line switches are recognized by MMC64:

• -32
• -64

If both of the preceding switches are specified on the command line, the rightmost switch is in effect.

Start-up considerations if -32 or -64 is in effect.

If MMC64 is started with no command-line parameters, or if MMC64 is started with the -64 switch, it executes as the MMC64 application. If MMC64 is started with the -32 switch, MMC32 is launched, using the same parameters initially passed to MMC64 (except the -32 switch), and MMC64 will terminate.

Start-up considerations if a console file is specified.

If the MMC64 command line does not contain a -32 or -64 switch, but the command line does contain a console file name, then MMC64 examines the console file before determining which version of MMC remains in execution. MMC64 uses the following algorithm.

1. If all snap-ins referenced by the console file are available in 64-bit form, then MMC64 will remain as the executing version (the remaining algorithm Steps are not executed). A snap-in is considered available in 64-bit form if it exists as an HKEY_CLASSES_ROOT\ CLSID\snap-in clsid\InprocServer32 key in the registry, where snap-in clsid is the registered CLSID for the snap-in.
2. If not all snap-ins referenced by the console file are available in 64-bit form, but all of them are available in 32-bit form, then MMC64 starts MMC32; MMC32 executes using the console file as specified on the command line, and MMC64 terminates (the remaining algorithm Steps are not executed). A snap-in is considered available in 32-bit form if it exists as a HKEY_CLASSES_ROOT\Wow6432Node\ CLSID\snap-in clsid\InprocServer32 key in the registry, where snap-in clsid is the registered CLSID for the snap-in.
3. If the number of unavailable 64-bit snap-ins is a subset of the unavailable 32-bit snap-ins, then MMC64 remains as the executing version (the remaining algorithm Steps are not executed).
4. If the number of unavailable 32-bit snap-ins is a subset of the unavailable 64-bit snap-ins, then MMC64 starts MMC32, and MMC64 terminates (the remaining algorithm Step is not executed).
5. If none of the previous Steps yields a conclusion, then a user interface is presented to the user, prompting the user to specify which version of MMC to execute (an option to cancel is also presented to the user).