On my shiny new Windows Server 2008 R2 installation, my monitors won’t go into low power mode even though they should turn off after 10 minutes of inactivity based on my display settings in Windows. Chris Rathjen suggested to me that it could be the wireless mouse (Microsoft Natural Wireless Laser Mouse 6000 in my case – what a mouthful) keeping it awake. I unplugged it from the USB port, and sure enough, my monitors went into low power mode.
So, I thought I’d try installing the current IntelliPoint drivers for Windows 7 64-bit to see if that fixed the problem. It did indeed do the trick. You can download it from http://www.microsoft.com/hardware/downloads/default.mspx if you are having a similar issue with a Microsoft wireless mouse.