I've written a set of batch scripts to do EXACTLY this. Machine has once script run before the image is made to make the newly imaged PCs prompt for the machine name ( we use the serial number) then it changes the SID, joins the domain, defrag's it's registry and page files, defrags \winnt then reboots ready to be shut down and placed on a user's desk and have the printer installed.

If anyone is interested I'll try to find them over the weekend (I've not got a copy to hand, but do in the images) I'm off on holiday on Monday so if I don't get round to it I'll try to remember to do it when I get back.