Windows might be turning off your network adapter to save power.
Turn off the power-saving option in the network adapter's properties
Open Network Connections by clicking the Start button-Control Panel-Network and Internet
Click Network and Sharing Centre-Manage network connections.
Right-click the connection, and then click Properties.
Administrator permission required If you are prompted for an administrator password or confirmation, type the password or provide confirmation.
On the Networking tab, click Configure.
On the Power Management tab, clear the Allow the computer to turn off this device to save power check box