Here it is, i used an udf from http://www.gwspikval.com/jooel/UDF/ by Radimus and changed it.


    Lpt1Printer()
    Function Lpt1Printer()
    Dim $index,$inst_printers,$PrinterPorts,$port_type

    $index=0
    $PrinterPorts="HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\PrinterPorts"

    :loopprinters
    $inst_printers=EnumValue($PrinterPorts,$index)

    If @error=0
    ? "$inst_printers"
    $port_type=ReadValue("$PrinterPorts","$inst_printers")
    ? "$port_type"
    If InStr("$port_type","LPT1")
    ? "lpt1 found"
    $=SetDefaultPrinter("$inst_printers")
    $FoundLpt1 = 1
    Return

    EndIf
    Else
    Return
    EndIf
    $index=$index+1


    GoTo loopprinters

    EndFunction

    If $FoundLpt1 = 1
    ? "Found Lpt1, dont install network printer"
    Else
    ? "No Lpt1, install network printer"
    EndIf


It will check the registry for the printers and their ports, then checks if any port matches "lpt1". If so, it will set the lpt1 printer default, else it does nothing.
Script works fine.