Systems Deployment

Guys
Im booting up a Dell Optiplex 760 machine with PXE boot , and I get to the Windows PE screen where it asks me to add my user name , password and domain so that the machine can be imaged using lite touch. But I can't get it to go pass this screen. I made a discover that I dont get an IP address , because I dont think the Windows PE is installing a correct driver for the model pc.
I do know it works fine as our other machines , Dell Optiplex GX260 works fine past this point.
Any one got any solutions what I need to do ?
I was having a look at this link
http://myitforum.com/cs2/blogs/rpedersen/archive/2009/04/04/importing-network-drivers-into-the-windows-pe-boot-image.aspx
Its seems to be pointing me in the correct direction , but I cant seem to find that window that he has to do does steps.