I have put 8 indentical Dell Optiplex into an office with the exact same setup on all. They share a HP 4000 via a JetDirect 170L. Six of the machines will print to which ever tray they select and the auto setting selects tray 2 because tray on is emply and closed. However two of the PCs will only try and print from tray 1 regardless of the settings. I have gone into the settings and told it to only select tray 2 and it makes no difference. The printer Just will not print. The only way to get it to print for them is put paper in tray 1. I have even shared a printer that works fine from one of the other PCs and the same thing happens when they try to print.