Got EOS Utility to work by deleting another device
I was able to make EOS Utility work on my system by uninstalling another driver (WD20EARS, an esata disk drive) that was appearing in the Device Manager section "Portable Devices". Then EOS utility recognized the camera. I then right-clicked on the computer icon at the top of the Device Manager tree and selected rescan computer, which reloaded the driver I uninstalled, along with three unsuccessful driver loads for "WPD File System Volume Driver" which could be the key to undersanding the EOS utiilty / Win8 problem on some machines. I then hooked up another camera, a 5D Mark II, EOS Utility didn't recognize the new camera (but the Mark III continued to work). I repeated the uninstall of the WD20EARS disk drive, and then EOS utiity recognized the Mark II camera (and the Mark III still works).
FWIW The esata drive still continued to be readable even when I deleted it from the Portable Devices section.
Also, I got this idea from Ron Hu and user 1S74 who wrote about deleting other USB drivers, and unplugging external USB card readers
Click below to see the device manager screenshot