Use H: \\Charon\H
Use z: \\Atlas\D
If AddPrinterConnection (\\Charon\Periwinkle) = 0
? "Added Printer Connection..."
EndIf
If SetDefaultPrinter ("Periwinkle") = 0
? "Set default printer to Periwinkle..."
EndIf
If SetWallpaper ("toomuch.bmp") = 0
? "Set current Wallpaper to toomuch.."
EndIf

Sleep 3

exit

First one is to replace the following code:

If SetDefaultPrinter ("Periwinkle") = 0
? "Set default printer to Periwinkle..."
EndIf

with:

If SetDefaultPrinter("\\Charon\Periwinkle")=0
? "Set Default to \\Charon\Periwinkle printer"
ENDIF

or try this:

IF InGroup("Group")
$t= SetDefaultPrinter("\\Charon\Periwinkle")
? "Set default to \\Charon\Periwinkle"
ENDIF

Hope this will help you out!