The whole thing started to lag, badly. From the early intro scene, main menu and throughout the gameplay. Even on the lowest settings, the game still lags. I'm very sure it's not my graphic card (nVidia GeForce 9800 GT 512MB) nor can I blame the game for the lag thingy. So I turned to my cousin and installed it on his rig, and this time with a strong nVidia GeForce 9800 GTX+. It can run on highest settings with no lags at all, not as lag like the one I'm having though.
So what I did was disabled the HID, "Human Interface Device". Go to Device settings and disabled the HID device that you won't be using in time. There's at least 15 HID devices and try disabling some of them, this should solved the lag problems but do be careful NOT TO DISABLE YOUR USB DEVICE PORT FOR MOUSE OR KEYBOARD. And there you go, the game will no longer lags, all settings maxed out and it runs perfectly fine.
Right click on my computer on your desktop and choose properties. Under those tabs or selections you should be able to open the device manager. This lists all the devices of your computer. One of the selections should be Human Interface Devices (HID). Click on the plus sign to expand your choices. Then you should be able to right click on each individual component and select disable. As I said before, you need to be careful not to disable your mouse and keyboard. Hope this helps.