The best graphics card for Pentium(R) duel-core E520 2.50 GHz 2GB RAM

With BIOS update that supports Core2 Quads. 8GB DDR2@800. I'm running GTX750ti O/C 2GB DDR5. Watch out for any new card that requires EUFI BIOS. Single slot cards that are long and thin, or short and wide can work. You need more RAM a video card is going to use some of it to store textures and wont leave much for the OS. Short dual slot cards work if 1/2 the bracket is cut off and the plastic cover is trimmed at the rear to let air go out the side towards the rear vents. With 65nm Core2 Extremes it can be overclocked to pretty high speeds. I'd add more RAM first, Then CPU, and them you can use a better video card. It has 4 phase VRM which is uncommon in a Dell and make it a good candidate for upgrades.