[Value data type] REG_DWORD [Description] If this policy value is set to 0, is absent, or any number other than 1 or 2, the effect on the Windows Installer depends on the operating system. On Windows Server 2003, Windows Installer is enabled for managed applications and disabled for unmanaged application installs. On Windows XP the Windows Installer is enabled for all applications. If this policy value is set to 0, Windows Installer is enabled for all applications. All install operations are allowed. If this policy value is set to 1, Windows Installer is disabled for unmanaged applications but is still enabled for managed applications. Non-elevated per-user installations are blocked. Per-user elevated and per-machine installs are allowed. If this policy value is set to 2, Windows Installer is always disabled for all applications. No installs are allowed including repairs, reinstalls, or on-demand installations. [Policy] 
DisableMSI