1) Type "bcdedit /set testsigning on" at an admin command prompt
3) Check to see if the desktop says "Test Mode" on the corners
(I'm not paying $300/yr for a kernel code signing certificate)
After that you should be able to install it like a normal driver. If adb seems to be freezing occassionally, try using adb_fixed.exe instead (don't forget to kill the adb server first).