In Windows 7 and Vista mapped network drives will disconnect themselves after a time and show a red cross on the drive icon. You will still be able to click on the drive and see/use the contents but applications that require a network drive will see them as disconnected and will not see files.If you try to disconnect the drive it will still sit there saying 'Disconnected Network Drive' - the only solution is to reboot.
This is because there is a default disconnect time for inactive network connections. To correct this and turn the autodisconnect off do the following:
Open the command prompt (as an Administrator)
In the Command box type:
net config server /autodisconnect:-1
and press return.
Reboot computer.
Your mapped network drives should now stay connected - this is a permanent fix.
Also - when connecting mapped drives to Vista or Windows 7 - connect them with the full domain name of the server i.e. \\servername.domain.local\sharename NOT \\servername\sharename - Vista/Windows 7 insist on full domain paths in order to reconnect. You can connect using just servername but if it needs to reconnect it will not find the server.
If the above fix doesn't work then try this:
1.Click Start , type regedit in the Start Search box, and then press ENTER.
2.Locate and then right-click the following registry subkey:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System
3.Point to New , and then click DWORD Value .
4.Type EnableLinkedConnections , and then press ENTER.
5.Right-click EnableLinkedConnections , and then click Modify .
6.In the Value data box, type 1 , and then click OK .
7.Exit Registry Editor, and then restart the computer.
WARNING - editing the registry incorrectly can cause your computer not to work properly or even not start at all - only try this fix if you are confident using regedit.
I.T. Tips from fergus.it