The only program I have to stop running in the background is Stardock's ObjectDock, due to a conflict with the DirectX drivers or something.
Othewise I never stop my background apps. I often have my chat client open, Chrome, anti-virus, and transferring photos from my digital camera all at the same time, on a 5 year old PC with a 3.0P4HT and whopping 1.5GB RAM.
I used to be paranoid and stop everything until I forgot one day, and then realized I didn't need to. This is the same while rendering.
Thank you Chienworks and Sonata....for your answer.
I have a brand new I7 920 quad . Running both XP prof and Vista home premium 64bits. I finally installed Movie studio 9 platinum. Bought last year.... couldn't installed it on my old PC.. I am back into editing... now with this new equipment HD geared....it is a bit like learning how to set up all over again.... I will try first with XP pro and move on Vista later on.... and probably will seek more help!!!!!