Using Ghost To Deploy Computers

I posted earlier regarding this topic, but can't find the NG I posted to. Essentially, we deployed a few identical machines (and hence identical HALs) individually. Now I'd like to save a ghost image, and use that to image each machine, then change their domain and workstation info. My only concern is this system ID thing - I was informed to use SysPrep, but what does that do? What happens if there's two SID's on the network - I was able to clone one desktop using ghost (didn't run sysprep), then just changed the computer name and joined it onto the domain after (had to reboot obviously for that, but I don't mind).