What kind of network are you working with? 10/100? Gigabit? Are the drivers that you are using only running at 10mbit half duplex? Why are you stuck with DOS? If using DS 6.9, you can download the WinPE setup files for free. This would make your life simpler, IMHO. Ghost? Rdeploy? A little description of your setup would also help. Are all the computers in a single room running off the same switch network? Using DHCP or PXE? I would start with the DOS drivers, make sure that you have the latest from the network card manufacturer.
HTH
Marco