The following tip is from https://www.techrepublic.com:
CHANGE DISCONNECT TIMEOUT FOR NETWORK SHARES
You might have noticed that even when you're connected and logged on to the network, some or all of your mapped resources show a red X beside the icon, indicating they're disconnected. This occurs because Windows NT and Windows 2000 both use a default resource disconnect time of 15 minutes. This automatic disconnect enables the server to recover server resources from idle connections. To reconnect to the share fairly quickly, simply double-click the icon.
This automatic disconnect behavior applies to Windows 2000 Professional systems that share their resources, as well as Windows 2000 Server systems. On either type of system, you can view the current server settings, including the automatic disconnect period, using the NET command. Open a command console and type the following command to view your current settings:
NET CONFIG SERVER
The Idle Session Time value indicates the automatic disconnect period.
To change the value, use the NET command again, as follows:
NET CONFIG SERVER /AUTODISCONNECT:
In place of , specify the number of minutes you want Windows 2000 to use for its idle disconnect timeout. Note that this value sets the amount of time the computer will allow idle connections to its resources before closing them, not the length of time you can have resources open on a remote computer. To disable automatic disconnect, set the value to -1.
