How to convert a combobox into a Checklistbox

private void Form1_Load(object sender, EventArgs e)
{
//See if any printers are installed
if (PrinterSettings.InstalledPrinters.Count <= 0)
{
MessageBox.Show("Printer not found!");
return;
}

//Get all available printers and add them to the combo box
foreach (String printer in PrinterSettings.InstalledPrinters)
{
comboBox1.Items.Add(printer.ToString());
}
}

private void button1_Click(object sender, EventArgs e)
{
//Create a PrintDocument object
PrintDocument pd = new PrintDocument();

//Set PrinterName as the selected printer in the printers list
pd.PrinterSettings.PrinterName = comboBox1.SelectedItem.ToString();

//Add PrintPage event handler
pd.PrintPage += new PrintPageEventHandler(pd_PrintPage);

//Print the document
pd.Print();
}

//The PrintPage event handler 
public void pd_PrintPage(object sender, PrintPageEventArgs ev)
{

//Get the Graphics object
Graphics g = ev.Graphics;

//Create a font Arial with size 16
Font font = new Font("Arial", 16);

//Create a solid brush with black color
SolidBrush brush = new SolidBrush(Color.Black);

//Draw "Hello Printer!";
g.DrawString("Hello Printer!",
font, brush,
new Rectangle(20, 20, 200, 100));
}
}