Why do network drives disconnect?

I have a Windows XP Home machine connected to several mappedd network drives on a Windows 2000 Professional machine acting as a server. The issue is that the mapped drives keep spontaneously disconnecting every 15 minutes or so. I have made sure that the power saving features have been turned off, i have modified the registry timeout and even implemented login scripts via a 3rd party application that allows such a thing with Windows XP Home Edition. Nothing has helped. Does anybody have any ideas? Notes from the Los Angeles Computer Repair Business Scene