Can't i share a wifi connected pc to another

Hello,

Please help me out ,, i m facing a problem regarding sharing the internet facility over 2 pcs one is connected to the internet through wi fi and is same connected to another pc through lan..
both the pcs have operating system windows xp sp2..
i want to use the internet connection on both the pcs through sharing the internet with the same wi fi connection ...
now answer me how can i do this is there any software required,,,if yes then which one ...