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Article ID: 104011 - Last Review: January 18, 2007 - Revision: 5.3

This article was previously published under Q104011

SUMMARY

You can modify user environment variables by editing the following Registry key:
   HKEY_CURRENT_USER \ 
         Environment
				
You can modify system environment variables by editing the following Registry key:
   HKEY_LOCAL_MACHINE \ 
               SYSTEM \ 
    CurrentControlSet \ 
              Control \ 
      Session Manager \ 
          Environment
				
Note that any environment variable that needs to be expanded (for example, when you use %SYSTEM%) must be stored in the registry as a REG_EXPAND_SZ registry value. Any values of type REG_SZ will not be expanded when read from the registry.

Note that RegEdit.exe does not have a way to add REG_EXPAND_SZ. Use RegEdt32.exe when editing these values manually.

However, note that modifications to the environment variables do not result in immediate change. For example, if you start another Command Prompt after making the changes, the environment variables will reflect the previous (not the current) values. The changes do not take effect until you log off and then log back on.

To effect these changes without having to log off, broadcast a WM_SETTINGCHANGE message to all windows in the system, so that any interested applications (such as Windows Explorer, Program Manager, Task Manager, Control Panel, and so forth) can perform an update.

MORE INFORMATION

For example, on Windows NT-based systems, the following code fragment should propagate the changes to the environment variables used in the Command Prompt:
   SendMessageTimeout(HWND_BROADCAST, WM_SETTINGCHANGE, 0,
    (LPARAM) "Environment", SMTO_ABORTIFHUNG,
    5000, &dwReturnValue);
				
None of the applications that ship with Windows 95 and Windows 98, including Windows Explorer and Program Manager, respond to this message. Thus, while this article can technically be implemented on Windows 95 and Windows 98, there is no effect except to notify third-party applications. The only method of changing global environment variables on Windows 95 is to modify the autoexec.bat file and reboot.

APPLIES TO
  • Microsoft Windows Server 2003, Datacenter Edition (32-bit x86)
  • Microsoft Windows Server 2003, Enterprise Edition (32-bit x86)
  • Microsoft Windows Server 2003, Standard Edition (32-bit x86)
  • Microsoft Windows Server 2003, Web Edition
  • Microsoft Windows XP Home Edition
  • Microsoft Windows XP Media Center Edition
  • Microsoft Windows XP Professional
  • Microsoft Windows 2000 Advanced Server
  • Microsoft Windows 2000 Datacenter Server
  • Microsoft Windows 2000 Professional Edition
  • Microsoft Windows 2000 Server
  • Microsoft Windows NT 4.0
  • Microsoft Windows NT Server 3.51
Keywords: 
kbhowto kbsyssettings KB104011
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