Disable OS/2 and POSIX Subsystems (Windows 2000/XP)

To conserve system resources you may want to prevent the Windows session manager (SMSS) from loading any optional subsystems, such as OS/2 or POSIX. This tweak can be used to disable these optional subsystems.

Warning : Make sure you use REGEDT32 to changes this value. Using Regedit may cause the system to crash.

Open your registry using REGEDT32 and find the key below.

When the OS/2 and Posix sub-systems are enabled the value called "Optional" will be set to "Posix" or "OS2 Posix". To disable those sub-systems double-click on the "Optional" value and delete the "Posix" data in the window.

Restart Windows for the change to take effect.

Note : The benefits of not loading these subsystems can be increased memory and system resources.

Registry Settings
System Key : [HKEY_LOCAL_MACHINE\SYSTEM \CurrentControlSet\Control\Session Manager\SubSystems]
Value Name : Optional
Data Type : REG_MULTI_SZ (Multi-String Value)
Value Data : Empty to disable OS/2 and Posix

Disclaimer : Modifying the registry can cause serious problems that may require you to reinstall your operating system. We cannot guarantee that problems resulting from modifications to the registry can be solved. Use the information provided at your own risk.