I downloaded the latest version of nLite and dutifully (and very carefully) followed instructions. Everything seemed to go fine and it burnt the image file, which I proceeded to test in a virtual machine. As my OEM copy began it's installation, everything was going great and then suddenly Windows rebooted and attempted to reload itself. That's when it gave me the following error, and stopped.

STOP: c000021a {Fatal System Error}

The Session Manager Initialization system process terminated unexpectedly with a status of Oxc000003a {OxOOOOOOOO OxOOOOOOO}

The system has been shut down.

SMSS.exe (the process that is failing, causing the bugcheck) is the process that is required to start all other user-mode processes on the system, and this loads immediately after the kernel to get Windows running. Those two error codes are supposed to provide valid data on the error, but since they're both 0x0 it's almost completely useless. Does this happen on every reboot after install? If so, you need to try installing with a clean source (if you haven't already) to make sure it works. Otherwise, it's something with nLite and you might want to try doing it again. This bugcheck is pretty much death, meaning you either remove whatever it is you just installed before the reboot, or, during a Windows install, you have to start over.