When I put my desktop computer into Standby, it comes out of standby all by itself just minutes later. I've also seen it come out of hibernation all by itself, but I've only tried that a couple times. Any idea why it's doing this? There isn't much going on in the background that I know of.
Some computers have the ability to let devices to wake them. These include network, usb devices, keyboard/mouse and bluetooth. Check in your BIOS or system settings that these settings are disabled
After following many suggestions, (BIOS, Scheduled Tasks, auto updates etc.) I finally solved the problem by denying the ability of the mouse to bring my computer out of stand-by.(Control Panel,System,Hardware,Devise Manager,Mice and pointing devices,power management).
Check to make sure "Wake on LAN" isn't enabled in the BIOS, data sent over the network can cause the PC to wake up. The windows event viewer will also have details of when PCs are waked.
Might be similar to my problem Desktop reboots itself on sleep or hibernate
you should identify your operating system and motherboard model as well.
I was wondering why this was happening on my netbook with Windows 7. It's a very clean install, so I know malware wasn't an issue, and I've seen Windows 7 be very reliable with regards to sleep in the past, so I had a hard time accepting that.
Turns out in my BIOS I have it set to wake on keyboard/mouse activity. At the time, I had a USB mouse plugged in, and moving that even a little bit waked the laptop.
Just something to look for if you have the same issue -- there might be no need to be paranoid.
Under Windows 7, check your power plan options and disable "Allow wake timers". That should do it.
After I tried all the methods knows related to wake-on-lan and network adapter, the unchecking of the "allow this device to bring out..." box from the mouse properties solved it for me.