Stores the values of environment variables that the system creates. These variables are used by Winlogon and Windows Explorer in Windows 2000 and Windows NT 4.0, and by Program Manager in Windows NT 3.51 and earlier.
To change the values of entries in this subkey, use System in Control Panel. Click the Advanced tab and then click Environment Variables. These entries appear in the System variables section.
The data type of entries in this subkey must be REG_EXPAND_SZ. If a user or application changes the data type, the system will not replace the variable with its intended value.
Use extreme care when changing these entries. If the operating system cannot find the files specified for a subsystem, you will not be able to run applications designed for other environments.