Windows 7 - Internet Connection Sharing Problem in Windows 7

Dear Friends,

I three pcs 2 laptops 1 desktop and when i try to share my evdo dialup internet connection in laptop with windows 7 it works fine but when i do same thing in my dektop pc it does'nt work even both have same operating system windows 7 professional there is nothing change in configuration please help me i want to share my internet connection in my desktop pc with windows 7..