I use both proTools LE and Sonar 4 Producer.. First off, Sonar is much easier to use and far more intuitive.. Why isn't it more accepted as compared to proTools LE..?

However, although I have a pretty powerful built computer, it seems to get hosed out and overloaded whenever I use a few poweful processing tools. I have UA's vintage card and it's supposed to run well because it's its own power source.. Still I get overloaded and it won't hold.. Suggestions?
I have P4 1gigDDR ram and it should be okay, no?