This batch file worked for me. Please see related links sections for additional info.
REM --- Check for an existing installation of Sophos AutoUpdate
if exist "C:\Program Files\Sophos\AutoUpdate\ALsvc.exe" goto _End
REM --- Deploy to Windows 2000/XP/2003
\\<SERVER>\InterChk\ESXP\Setup.exe -updp "\\<SERVER>\InterChk\ESXP" -user "USER" -pwd "PWD" -mng yes
REM --- End of the script