On a mobile PC that is running Windows 7, you create a task in Task Scheduler and select the Wake the computer to run this task option. When the mobile PC enters the sleep mode, it does not wake up to run the task at the scheduled time.
By default, the ability to wake the system from sleep for a timed event is disabled on Windows 7-based mobile PCs. Programmed timed events do not wake the system regardless of whether the mobile PC is on AC or on battery power. However, you can change the Power Options settings to enable the wake timers.
To change this behavior, follow these steps.
Note Your mobile PC may wake up for tasks under some unexpected circumstance. For example, your mobile PC may wake up when it is in a bag or in a thermally constrained environment. We recommend that you evaluate the issues that may occur before you change the settings.
Click Start, type power options in the Start Search box, and then click Power Options in the Control Panel list.
Click the Change plan settings option that is next to the power plan that is selected, and then click Change advanced power settings.
Expand Sleep, expand Allow wake timers, and then select Enable.
This behavior is by design.