|"i insert new 2gb RAM for good performance when i play game"|
RAM isn't going to help your gaming performance very much, you need a better video card. The 210 is a low end HTPC card, not a gaming card.
"i dont understand what is the problem"
We need to know the make/model of your motherboard & more details about the RAM you bought. Is it DDR2-667, DDR2-800, DDR2-1066? What is it's default voltage? It should be 1.8v but some RAM is rated between 1.9v-2.2v. If that's what you have, you'll have to manually configure the memory voltage setting in the BIOS. Also, you should probably be running a matched pair of RAM to enable dual channel mode.