I doubt you can install software using a normal account on a machine joined to a domain if no group policies authorize software installs. If you have domain admin credentials, you can either create a GPO with either a startup script for any domain authenticated user or use PSEXEC if remote admin shares are enabled:
psexec \\HOSTNAME -u DOMAIN\user -c -f c:\WINDOWS\system32\robocopy.exe "\\share\Path-to-OCSNG-Windows-Agent-2.1.1.1" "C:\temp\OCS" OCS-NG-Windows-Agent-Setup.exe
psexec \\HOSTNAME -u DOMAIN\user -c -f c:\WINDOWS\system32\robocopy.exe "\\share\Path-to-OCSNG-Windows-Agent-2.1.1.1" "C:\temp\OCS" cacert.pem
psexec \\HOSTNAME -s C:\temp\OCS\OCS-NG-Windows-Agent-Setup.exe /S /NOSPLASH /NO_SYSTRAY /NOW /ca="cacert.pem" /SERVER=http://ocshostname/ocsinventory