(Untested)
Code:
 
IF @WKSTA="TS-SERVER"
  $User=ReadValue('HKEY_CURRENT_USER\Software\GoldMine\GoldMine Link for Microsoft Outlook','GMUserName')
  If $User='NONUSER'
    Shell 'regedit /s "\\MAIN-SERVER\Support\Goldmine\GISMO\GISMO.reg"'
    ?"GISMO Installed for " + @userid
  Else
    ?"GISMO Already Installed for " + @userid
  EndIf
EndIf


Looks like you were missing an "=" after If $user and an Endif at the end.