i just started playing far cry yesterday the graphics are stunning and it runs smoothly until i shoot someone then it lags, i have a gainward 5900xt golden sample but i only got 512mb of ram, was wondering if increaseing the ram to a gig would help this prob?

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Mobo: Gigabyte K8N SLI-Pro nForce4
CPU: Athlon 64 X2 4200+
Memory: 2048Mb Crucial DDR 3200
GPU: Gainward 7900GT 256mb
HDD: 2x 120Gb SATA Diamondmax 9
Sound: Audigy 2 ZS
PSU: Hiper 580W Type-R Modular
Optical: NEC 16x Dual layer DVD-RW