Well, for starters, your machine is going to be more inclined to have problems than say, mine would with such a card. You have a P4. This means You also have an INTEL Mother Board. Right away there is a "Lack of Perfect Compatibility". If your going with a Nvidia Video Card, its always best to get a Nvidia Mother Board. (nForce2). Always start with Nvidia for gamers.

Another thing, it sounds like you dont have enough RAM, or your memory is failing or something perhaps.