IAM USING PENTIUM-4(524) 3.06 GHZ, 2GB RAM, GIGABYTE GA-G31M-ES2L MOTHERBOARD, WINDOWS VISTA ULTIMATE SP2 OPERATING SYSTEM, THIS BOARD HAS VGA GRAPHICS ACCERALATOR. IT HAS A SLOT OF PCI EXPRESS X16 DDR2, AND I WANT TO UPGRADE WITH 512MB GRAPHICS CARD. I DONT KNOW WHICH CARD WILL SUITE THIS BOARD. SO PLEASE KINDLY ASSIST ME GET RIGHT PRODUCT.
Your CPU is extremely old and insufficient for most current games. Fortunately your motherboard isn't as old and can use Core 2 Duo processors. In the US it will cost you $50-70 to upgrade to a dual core CPU that will be acceptable for gaming. Something like an E5700 would be a nice choice. http://www.newegg.com/Product/Product.aspx?Item=N82E168...
Or if you can afford it you can get a quad core processor such as this; http://www.newegg.com/Product/Product.aspx?Item=N82E168...
As for the video card we really need more information like what power supply is in your system, the native resolution of your monitor and approximately how much you are willing to spend.
Firstly please do not type in CAPS as it signifies shouting.
Also with regard to your existing configuration, it is quite old and if a high end card is put, it will be bottle necked by your processor. So get yourself an AMD 5670 or if you can, do get the AMD 6670. Unless your PSU has got extra power connectors for graphics cards, stick to the 2 cards mentioned above. They are the fastest cards that can be put in your machine with your current config.
An extra 2GB of RAM will help your machine to run newer games quite comfortably.
Oh, also if possible, please upgrade to W7. Vista sucks. Big time.