Windows System Environment Variables

%SystemDrive% C:
%SystemRoot% C:\WINDOWS
%WinDir% C:\WINDOWS
%SystemDirectory% C:\WINDOWS\System32
%ComSpec% C:\WINDOWS\system32\cmd.exe
%programfiles% C:\WINDOWS\Program Files
%Temp% C:\Documents and Settings\Usr\Local Settings\Temp
%HOMEDRIVE% C: The drive letter associated with the user's home directory
%HOMEPATH% The path to the user's home directory (excluding drive): \Documents and Settings\Guest
%OS% The operating system the user is running
%USERDOMAIN% The name of the domain that contains the user's account
%USERNAME% The user's name
%USERPROFILE% C:\Documents and Settings\Usr\
%USERPROFILE%\Desktop The user's desktop folder