I have been going t msconfig and startup menu and then disable all.Is this the same

Disabling things in MSCONFIG's window doesn't shut them down. It prevents them from starting the next time you boot your computer. There may also be other processes that are started from the Start -> Programs -> Startup folder.

Probably for one-shot shutting things down without using other software it's easy enough to do the Ctrl-Alt-Delete thing and end task everything but Explorer and Systray.

Having other processes running while rendering probably makes very little difference in the rendering time. Unless you have some other very processor intensive programs running the difference in rendering time will be very minimal. I usually have a dozen other things going on on my computer while i'm rendering: browsing the web, word processing, editing other movie projects, even other renders. I'd rather not waste all that computer time while it's rendering by not being able to do anything else with my computer.

On the other hand, it's quite important to shut these other programs down while capturing or printing to tape, especially if you have a slower computer.