Bcz I am considering these two for now as long as the 6XXX series from AMD is not released,would like to know about this game. have seen its videos.looks stunning. how much stressing it is for the GPU?
Then you're going to have issues. That is what I used to have (I'm assuming it's the dual-core).
I was lucky to get 20 fps on that and I had a worse GPU than you: HD3870. When I upgraded to my current CPU (AMD Phenom II X3 720BE), my fps jumped to around 35 fps. When I then upgraded to the 5750, I was getting an average of 40. With my over clocking, I'm around 45 now.
So, I don't know how well a 5770 will work with the 4200+. My guess is, not much. You might get better FPS than I did, but I don't know.
You really need to upgrade your CPU to a tri or quad-core CPU because GTA IV was written to take advantage of the extra cores. Dual-cores just don't cut it very well with this game.
Just recently installed and been playing GTA: Episodes from LC from my MSI 460 Hawk, no OC, and get around 40fps. I'll check when in front of the machine to confirm. Sorry, no experience with the 5770. Other specs listed in sig.
One thing to remember about episodes is they've optimized them better than the original GTA IV.
Also, for GTA IV, download the latest patch for it. I believe that will bring it within the same realm as the Episodes releases as far as optimization goes. It definitely gives you finer control over the details.
But in the end, I still believe that the 4200+ is going to limit you. You really need to go to an Athlon II or Phenom II with at least 3 cores to really get acceptable performance.