choppy display

[KingTKS]

i built a computer for my church and its amazingly fast and awesome. I have a radeon x1600pro. X2 4400+. and 2GB of corsair Value ram pc3200. The main purposes of this computer are to Do video stuff. such as video editing primarily adobe premier and pinnacle studio 10. but its main purpose is to use it for mediashout which if you don't know its a presentation type thing like power point only way more advanced. it requires dual screen and we use a projector to show the stuff on the wall. this is where my problem is. the computer seems to be running quite sluggish when changing backgrounds and slides. like its chopppy almost feels like the processor is spiking up and down. also when i launch big programs such as premier and pinnacle the computer gets choppy instead of a smooth launch. like the mouse starts jumping all over the screen. usually its fine once its fully launched but the media shout problem is a big concern. any ideas on whats doing this? video card? cpu? memory? last note we are using s-video from Graphics card into the projector.

thanks for the help
King