The Windows directory or SYSROOT. This corresponds to the %WINDIR%
or %SYSTEMROOT%
environment variables. A typical path is C:\Windows
.
This variable points to the Windows directory (on Windows NT-based operating systems it is identical to the %SystemRoot% variable. If the system is on drive C:, then the default values are "C:\WINDOWS" on Windows 95, Windows 98, Windows Me, Windows XP, Windows Server 2003, Windows Vista, Windows Server 2008 and Windows 7.
For more info see Wikipedia's Environment Variables entry.