Why do you ask for input via a command window when you are using a KiXforms graphic interface?
Code:

;x is the variable that represents the user's choice of printer
Dim $X
Get $x

I presume you want to change this:
Code:

$PrinterChoices.Width = 400

You get the background image and the driver from the same computer I presume. I think there is a typo.
But I also presume this is a workstation. Doesn't the 10 computer limit also goes for this one?
Code:

$panel.BackgroundImage = "\\s096-a0290-01\sch030$\printers\matthew.jpg" 
...
AddPrinter("10.48.18.1","Lexmark T640","\\s096-a290-01\sch030$\printers\t640.inf","Library Printer",0)