Computer half-waking up and going back to sleep on its own

I have a rather strange issue with a Windows 7 Desktop. This computer will partially wake itself up from sleep and go back to sleep. When it partially wakes up, the fans spin up, the case lights come on, hard drives spin up, and USB devices receive power for a brief period of time. The displays never come on. After about 2-5 minutes, the computer goes back into sleep. It does this about every 45-60 minutes.

If I move the mouse or hit the keyboard while the computer is in its half-awoken state, the computer doesn't do anything different. It doesn't fully power back up and it resumes putting itself back to sleep after a couple of minutes. Because of this, I can't use the "powercfg -lastwake" command to track what is bringing it up.

However, if the computer is fully asleep (nothing spinning or on), then I have to use the power button to turn it back on. The keyboard will not wake it up, even though the keyboard is shown as a registered device to bring the computer out of sleep (confirmed from powercfg command in command prompt).

I apologize if this is somewhat confusing, but I've been searching around for the past few days trying to find a resolution. I am confident it isn't malware related, as this computer is scanned with Malwarebytes and Security Essentials twice a week (nothing detected in quite some time).

Things I've tried:

Adjusting power settings to turn off hard disks and display after 20 minutes, put computer to sleep after 60 minutes
Disable the mouse from being able to wake the computer from sleep through elevated command prompt
Double checked that the network adapter is not able to wake the computer from sleep
Disabled magic packet wake for network adapter


Any thoughts? Suggestions?

Thank you ahead of time!

This might be of no actual help, but my Windows 7 Home Premium, for about 7 days, woke from sleep just as your first paragraph, except my machine did that every 20 minutes or so. It started after I got it back from my small local computer shop that built it last March, it having developed several glitches (but I was able to use it). The glitches were more or less fixed. The waking up and going to sleep problem disappeared of its own accord.

Is this a new/recent problem, and sleep worked ok before ?
If it's new problem, do you have a restore point or backup image from before this problem started ?
If you do, can you restore and fix the problem ?

If that doesn't help, work though this tutorial:
Power Options and Sleep Mode Problems

I have a wake-up problem if i don't get enough cups of hi-test coffee

I tracked down the issue.... and it was purely on a fluke. There was a faulty Mini-USB cable attached to the back of the computer that was just hanging there not being used. I walked in Friday evening and the computer was making the USB Disconnect / USB Connect sound over and over in quick succession. When troubleshooting that, I found the cable just hanging there. After I pulled it, the connect/disconnecting stopped. Since then, the computer hasn't been coming out of sleep on its own.

Man.... 4 months of the computer doing this, only to be caused by a (faulty) rogue USB cable.

Oh well... Problem solved!