Hello Mahesh,
We would like to inform you that since the chipset is embedded into the motherboard it cannot be physically removed or replaced as you are looking for.
Can i use a new graphic card externally............??
Because i cannot play MostWanted or any games with the present Graphic card
Of course you are not able to play any game with your present configurations.
PLS don't tell me that you are trying to play Need for Speed Most wanted 
. Come on man that game requires a much more powerful PC
You have the option of adding more RAMs "Highly recommended" to your present RIG & surely you can add an external graphic card. With your current CPU you can go for something like a 9800 GTX or a little bit higher. Anything more will bottleneck at your CPU. Besides, it all depends on your budget.
Bear in mind that this upgrade is fine but it is still the minimum required to play games. Yet, you will see phenomenal performance.
Advice:
Update to Win7 64 bit if you added more rams
Send me your Motherboard vendor & some more details & we'll take this one at a time
I also want to update my video card. Many hd game run slow. Any advice?
Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz (4CPUs), 2.4GHz
4 GB Ram 500 GB hardrive
Windows 8 pro 64 bit
DirectX 11
Intel(R) G33/G31 Express chipset family
That is an integrated video controller so in that case it cannot be replaced or swapped for another one. If you would like to still continue using an integrated video controller you will need to change the motherboard in the computer you have.
If you would like to have information on what hardware can be installed or upgraded in your system, then please check directly with your motherboard or computer manufacturer.
