Pentium Celeron D 2.8GHz and Games

Hey people, how would a pentium Celeron D 2.8Ghz along with a nvidia 5500 FX 256 ddr mb and 512 mb of ddr ram run some of the newer games like Doom3, HalfLife2, or FarCry? I’m on a tight buget and I need to upgrade my processor. Thanks for any helps or recommendations.