[顯示卡] Why when i play a game it lags

sonofgun

the game i play is
Call of Duty 2
and my GPU is onboard Nvidia 6150SE
any ideas that why it lags?

sonofgun

I just installed a new GPU

mobo: ECS MCP61PM-AM
AMD 64 X2 5000+ 2.6GHz
3GB RAM
Thermaltake 500W PSU
EVGA 8800 GT 512mb DDR3
400 GB SATA HDD
Optiarc DVD RW 20X

Can you tell me how long can I play with this spec
(As in how long this PC will last compare to the latest modern games)

THANK YOU