Win2K doesn’t let XP machines access shares

Our office has predominently XP (some home, some pro) machines. However, we have one older PC that has Win2K loaded. It runs great right now, but will probably bog down if I try loading XP on it. It has no problem accessing the shares on the XP machines, but the others can’t access its shares. I set the shares to be accessed by “everyone”, even created a user/pass that other PCs can use. Are there any compatibility issues or settings I need to be aware of?
Thanks
Rich