Do you find that your Windows 7 computer wakes up from sleep unexpectedly at a particular time every day? If so then you might to check up if any scheduled tasks are waking your PC up.
To do so, click Start > All Programs > Accessories > Systems Tools > Task Scheduler > expand Task Scheduler Library.
Check here to see if any programs are schedule to perform task which require your PC to be woken.
Many a times, the Windows Media Center automatic update function is found to be the culprit.
To check this, expand Microsoft > Windows > select Media Center > mcupdate_scheduled
Double click mcupdate_scheduled to open its Properties box.
Edit the trigger and from the drop down menu, select when you want to Begin the task.
You may select it to check only at Windows start up.
If you do not wish to fix it manually but would instead like Microsoft to Fix It for you, so that Windows Media Center checks for updates only at, say, logon, then download and apply this Fix It 50448 solution.
This Fix It solution will enable the update check at log on only.
This Fix it wizard may be in English only but it also works for other language versions of Windows 7.
See this if your Windows 7 does not go to sleep.