A couple of things here. If you are running OEM licenses, you technically cannot just take an image off of one machine and place it on another. In doing that, you are breaching the EULA as the specific license (product key) is tied to the hardware it was purchased with and is non-transferrable. What you are doing is using the same product key over and over and over.
That being said, if you are against using sysprep or wish to continue doing it this way, you can either still use ghostwalk (just have to copy the command and execute it in a script, or you can use a sysinternal product (now owned by MS) called newsid.exe.
I would suggest that you download the latest sysprep and run through the wizard and read the documentation on M$'s website.