A couple days ago, I watched my PC wake from sleep mode by itself. Yesterday, it was already awake when I got up. This morning, I was awakened by the bright monitor turning on around 4:30 AM. I've never seen this before in the couple months since I built this PC. The most recent hardware/firmware change was upgrading BIOS from 4507 to 4752 about 2-3 weeks ago. But my PC and I had at least two weeks of uninterrupted sleep (couldn't resist the double entendre) after the BIOS update, so I'm not sure that caused it.
Wake/Sleep Settings: Basic power settings are turn off display in 20 mins., computer sleep in 30 mins., hard disks off after 45 mins. The Intel 82578 network adaptor was set to wake on magic packet. I disabled that, but I'm skeptical about something on my home network accidentally sending the correct magic packet. I also disabled Allow Wake Timers. That didn't help either. Any other ideas?
I'll post this issue on some Windows 7 sites too, but want to check BIOS/firmware first.
OS: Windows 7 Pro x64
Motherboard: Intel DP55KG
CPU: i7 860
Storage (system): Intel X25-M G2 80GB SSD x 2 (RAID-1)
Storage (data): Samsung F3 HD103SJ 1TB x 2 (RAID-1)
Solved. I discovered a wake timer event in System event log:
The system has resumed from sleep.
Sleep Time: ?2010?-?03?-?16T04:51:52.023330900Z
Wake Time: ?2010?-?03?-?16T07:04:08.353048800Z
Wake Source: Timer - Windows will execute '\Microsoft\Windows\Media Center\mcupdate_scheduled' scheduled task that requested waking the computer.
This alerted me to the existence of many scheduled tasks--most of them hidden--that I disabled or rescheduled in Windows Task Scheduler to stop the PC from waking up in the middle of the night. You can also control whether events are allowed to wake the computer. Note that, for some reason, disabling wake timers in Windows 7 advanced power management didn't stop these tasks from waking my PC.
Update Check (changed from daily at 2 AM to every 4 weeks at 2 PM)
Microsoft Windows Application Experience AitAgent (disabled) ProgramDataUpdater (disabled)
Customer Experience Improvement Program
Defrag (changed to 7 PM instead of 2:30 AM)
Diagnosis (changed from 1 AM to PM)
WinSAT (changed from 1 AM to 1:30 PM)
mcupdate_scheduled (changed from 7:13 AM to 11:13 AM)