p4 1.5 gb ram windows xppro latest version of vegas4

I have optimized XP and when I edit only vegas runs with a minimum of drives - no network cards, virus scanners, etc

I will get either low memory errors then a system hang - or it will glitch - coming off a supersample part the audio stays synced, but the picture freezes then will snap to the proper place, but I loose whatever amoutn of screentime it hangs for

I'm at my wits end