First the question; How do I figure out what is preventing my Windows 7 computer from going into sleep mode?

Second; some background...

I've been struggling with this for a few days and am utterly perplexed. I setup sleep mode on my Windows 7 PC a few weeks ago, and all was well. The PC would sleep as expected and I was snuggly in knowing that my computer was saving power and some wear and tear on the components (we'll leave the 'is it better to sleep' debate for another thread/day, please don't start it).

Well, I noticed the other night that my system stopped ever going to sleep. I set the sleep time down to 1 minute and wandered fully away from the PC (ensuring that no errant mouse or keyboard movements would occur) and the PC never went to sleep. I've also observed this over longer intervals as well, such as overnight.

• I have sleep mode enabled, of course
• "multimedia settings - When Sharing Media" is set to allow the computer to sleep.
• "powercfg -lastwake" show nothing of interest, since it never goes to sleep and can't wake up.
• "powercfg /requests" shows 3 entries - all "[DRIVER] ?". I assume that 2 of these are my mouse and keyboard - as I've recently used them to run the powercfg command. I'm at a loss for the third though.
  • I've unhooked all USB peripherals save for my keyboard and mouse.
• Wake on LAN is disabled in my BIOS.
• I know that you can disable all apps from waking/preventing sleep - but I want the ability to remain for those apps that do legitimately need to keep the system awake.

So; does anyone know of a way to figure out what the 3rd phantom "[DRIVER] ?" is in powercfg /requests?