Wednesday, March 3, 2010

Windows 7 system waking up at night

A common reason for a computer to wake up is that a network interface was configured to Wake on LAN (WoL) (usually company computers) – that means it can wake up due to a link change signal or a Magic Packet. This feature can be quite useful if you want to wake up your work computer, first logon through the company VPN and then run a WoL software from one of the Citrix / Terminal Server sessions (usually WoL packets are not allowed through gateways from the Internet). Nowadays even wireless network devices allow for WoL (depending on BIOS and motherboard).

To disable (or enable) WoL, see this article below for more details – simply check/uncheck the the box that says “Allow this device to wake the computer” accordingly. The “Only allow management stations to wake the computer”  I believe it means to wake up only on Magic Packet requests.

Another reason for your Windows system waking up, and probably more common to Windows 7 editions including Media Center (e.g. Professional), is that if the computer supports APM 1.2 or later it is possible to have tasks that can wake up the system from S4 (Hibernation) or S5 (Power Off) – most common seems to be the case with the Media Center Update scheduler task – see more details below.

Notice the “Wake the computer to run this task” is checked - either uncheck the box (double click the task scheduler entry to edit) or simply disable the task altogether.

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