astrallite :
Unless the game has a menu feature for that, you won't be able to achieve it.
Even so, stereo headphones have only 1 driver, meaning its point-source, and can only vary in sound amplitude. Any "emulated surround" speakers/headphones will have multiple drivers.
His Sound Card MUST have capability to "Emulate Surround" too.
@makua
You MUST fit on all the 3 points here:
1.The game must have a menu feature for that(Emulated Surround OR 3D Sound OR Surround, any of the these should work for what you want)
2.Your Headphone must have multiple drivers(some headphones have that)
3.Your Sound Card must have capability to Emulate Surround.
Without ANY of the 3, your attempt will just be in vain.