As much as it pains me to say this. I have been having some great results using Windows Defender Offline. It cleaned a machine for me a few days back that nothing else would touch.
Download the correct version, burn to a CD then boot the machine up from the CD, make sure the machine has an active internet connection so the app can update the virus signatures. I have both 64bit and 32bit versions on CD and it soon tells you if you have booted with the wrong version (saves starting the machine up to discover what version of Windows is installed).
What is Windows Defender Offline?