Registry key for system variables:
HKEY_LOCAL_MACHINE\ SYSTEM\ CurrentControlSet\ Control\ Session Manager\%SystemDrive% = C:
%SystemRoot% = C:\WINDOWS
%WinDir% = C:\WINDOWS
%SystemDirectory% = C:\WINDOWS\System32
%ComSpec% = C:\WINDOWS\system32\cmd.exe
%programfiles% = C:\WINDOWS\Program Files
%Temp% (or %Tmp%) = C:\Users\<USERNAME>\AppData\Local\Temp or C:\DOCUME~1\<USERNAME>\LOCALS~1\Temp
%HOMEDRIVE% = C:
%HOMEPATH% = C:\Users\<USERNAME> or C:\Documents and Settings\<USERNAME>
%OS% = The operating system you are running
%USERDOMAIN%
%USERNAME%
%USERPROFILE% = C:\Users\<USERNAME> or C:\Documents and Settings\<USERNAME>
%USERPROFILE%\Desktop = C:\Users\<USERNAME>\Desktop or C:\Documents and Settings\<USERNAME>\Desktop
%CD% = The current directory
%DATE% = Current date in the format set by the Date command
%TIME% = Current time in the format set by the Time command
%ERRORLEVEL% = A number defining exit status of a previous command or called executable
%RANDOM% = A random number between 0 and 32767
Registry key for user variables:
HKEY_CURRENT_USER\Environment