Pent D840, 8800GTX, & Lost Planet @ 1280x1024...a joke?

I know that a Dell XPS600 (Pent D 840 (3.2Ghz) with 2GB of RAM) is quite laughable by many of your standards. I currently have this machine as an extra rig with a nVidia 8600GT on XP 32-bit. The 8600GT is not doing well, at all, in Lost Planet, even @ 1024x768...pretty bad stuttering.

However, I also have a 8800GTX in my Vista rig (described in my sig). I'm considering moving the GTX to the Dell to see if it would give me a fluid experience @ 1280x1024. Is this a waste of time because the yesteryear processor is going to bottleneck to the point that it may not be usable or could this be a promising endeavor in your opinion. The Vista rig is not doing well in Lost Planet...doesn't start often, and now, I can't save after killing one of those dreadful bugs.

When it does start I can game @ 1920x1200 or 2560x1600 (so, its okay when it is actually working) ...could be the rig, could be the game, but I wanted to try LP on another machine, ...but wanted to get opinions on whether or not its just a waste of time to put the GTX next to a Pent D 840 hoping for descent fps @ 1280x1024.