If you've used SMS/SCCM for very long at all it's likely that you've run across a situation where you need to manually execute an install as the local system account for testing purposes. You probably went to your favorite search engine and found a couple methods for start cmd as local system. Those methods likely used a scheduled task or a service to kick off cmd. While those processes to work I find them somewhat convoluted and I can't remember the steps required so I have to hunt them down each time I need to perform them. Here's an easier way to get to cmd as local system using PSExec. Just download PSTools and extract them to a location that's in the system path and run PSExec.exe -i -s -d cmd.exe The command window that opens will be running as local system, from there you can execute anything that you want to to mimic what SCCM would do from a package.
If you don't already have PSTools download them from here:
http://technet.microsoft.com/en-us/sysinternals/bb897553.aspx