Network Auto-Disconnect

Windows has a network auto-disconnect function that will do an OSI Layer 1 disconnect after 15min, to save power presumably. This can cause problems with certain applications, namely Outlook in some cases - that will start doing some strange things and will return to normal only after restarting the program.

A solution is to disable this feature by running the following in an administrator cmd session.

net config server /autodisconnect:-1

To make it permanent we need to edit the registry:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\lanmanserver\parameters
There should be a dword named "autodisconnect"
Set the value to 0xFFFFFFFF

Source URL: http://www.windowsitpro.com/article/john-savills-windows-faqs/how-do-i-configure-lan-autodisconnect-.aspx