problem on networking XP & 2000 server

im trying to make a network of laptop with xp pro & win 2000 server desktop but i m not able to make them communicate in workgroup but when im trying to make it on domain it works. im not been able to understand the problem. one of my friend who is working as administrator in a company says that u can’t make a network. if it is true can any one give me a proper answer for that reason. thanks