Operating System: Windows Vista™ Ultimate Service Pack 2
System Manufacturer: BIOSTAR Group
System Model: G31-M7 TE
BIOS: Default System BIOS
Processor: Intel(R) Core(TM)2 Duo CPU E7400 @ 2.80GHz
Memory: 2046MB RAM
using a atx 450W as power supply
need to improve and to add a new graphic card any sugestion???all are accepted
So standard no-name PSU. If it says 450W that means that the normal operating wattage is 300-350 max. That limits your choices a lot, because with a crappy PSU no one can recommend you anything really good. I say ATI 4670 or ATI 4770 (this one is so and so because it requires 1 extra power connector so that will be pushing it). If you really want a card that can push current games almost to the max I suggest first upgrading the PSU to a decent brand 450W unit (Corsair, Antec, OCZ, etc) If you can do that and have a good budget the best for your resolution is the ATI 5850. If that is too expensive get the 5770 or 5750.
Well, if you get a new powersupply, say a good brand name of 450w+, then you can start looking at cards. I wouldn't recommend anything over an ATI 5770, as the rest of your system will hold it back. Unless of course, you are planning on upgrading part by part over time, then a 5850 could be ideal, but a hell of a lot cheaper by the time you might be able to actually use its power.
No one outside of a diehard Nvidia fan would recommend buying a green team graphics card right now. You will spend far too much money on a card that doesn't have the features to match its direct competition. If you are intent on Nvidia, wait for the new cards to come out. If you want kickass top shelf graphics right now, or at least the best bang for your buck, ATI is the only way to go. That could be different in 2-3 months, but for right now, that is just how it is.