Single Application Mode Background Tasks

Hi,
I was reading the Business Edition documentation and will likely experiment with Single Application Mode since we just have a couple windows apps we want to get running. I'm wondering though if there are any technical write-ups on how exactly it works. I'm particularly interested in background tasks such as Microsoft Monthly Rollups, Virus definitions, etc: do these simply not happen? Or is full Windows running, including all the background services, and just hidden to the user?
Thanks,
Jeff