Network Help

i need to setup something similar to a server where computers can exchange files and save on a computer remotely i also need to have it setup with users being able to log in with their files on different computers in the office

what should i do? i have windows xp and windows 2000, i need to have the user computers with windows xp could i use xp to make a server or could/should i move to another os for what i want to be the main computer with all the files