Also try updating your drivers, everything from your Graphics to chipset to Sound drivers, I am running a Asus G74SX and I am not having any lag problems even playing Crysis Warhead on everything set to GAMER or Metro 2033 and Diablo III in my screens native 1920X1080 resolution. Infact Diablo III automatically sets the graphics to Full-HD!
Asus G74SX-FHD-TZ130V
2nd Generation Intel Core i7-2630qm 2ghz With Turbo Boost Up To 2.9ghz CPU | Metallic Keyboard | Win 7 Home Premium | Blu Ray & DVD +/- & CD Player | 4 USB Ports | Media Card Reader | Webcam | Bluetooth | WIFI | Nvidia 3D Vision GTX560M 3GB | 2 X 750GB 7200rpm HDD's | 8 GB RAM DDR3 1333mhz | 17 Inch Screen 1920X1080 Resolution | 1 HDMI Ports | 8 Cell Battery