窗体上有个TComBox，命名为cb1

窗体名为Form1

procedure TForm1.FormCreate(Sender: TObject);

begin

 cb1.items.assign(printer.printers);

end;

procedure TForm1.Button1Click(Sender: TObject);

var LPrinter:string;

   PrinIniFile:Tinifile;

   LStr:string;

begin

 LStr:=printer.Printers[cb1.itemindex];

 delete(Lstr,pos(' on ',Lstr),Length(LStr));

 PrinIniFile:=TIniFile.Create('WIN.ini');

 try

   LPrinter:=PrinIniFile.ReadString('Devices',LStr,'');

   PrinIniFile.writestring('windows','device',LStr+','+LPrinter);

 finally

   PrinIniFile.free;

 end;

end;

***********************

uses printers;

procedure SetDefaultPrinter(const printerindex:integer);

Var

   FHandle :    THandle;

   HPrt    :    THandle;

   PrtInfo5:    PPrinterInfo5;

   FDevice:     array[0..79] of char;

   FDriver:     array[0..79] of char;

   FPort:       array[0..79] of char;

begin

 {printerindex为选中打印机的索引，如果使用打印机名称，则此句可忽略}

 Printer.PrinterIndex := printerindex;

 Printer.GetPrinter (FDevice, FDriver, FPort, FHandle);

 OpenPrinter(FDevice, HPrt, nil);

 if HPrt = 0 then

   raise(Exception.Create('不能打开打印机'));

 try

   PrtInfo5 := GetPrinterInfo5(HPrt);

   PrtInfo5.Attributes := PrtInfo5.Attributes +

       PRINTER_ATTRIBUTE_DEFAULT;

   SetPrinter(HPrt,5,PrtInfo5,PRINTER_CONTROL_SET_STATUS);

   FreeMem(PrtInfo5);

 finally

   ClosePrinter(HPrt);

 end;

end;