offline and online gaming

how can i setup both offline and online gaming using LAN because i tried it and only online gaming works.
the problem is when i start using a program that is an offline game the server is seen but the players cannot enter the game.. what should i do? all my offline games cannot connect to the server.. pls. help me... and lastly i'll add this problem about a driver sigma geforce4 mx 440 with agp 8x i do not have this driver and i cannot find it it takes me 5 months yet i cannot stilll find it. pls. help me...