I know this post is quite old, and my phone is a Nokia Lumia 520 and this thread is for the HTC, but my solution might help someone else.
I had been attempting to install the latest Windows Phone 10 preview and after I thought the process had completed, I tried to turn my phone on. Initially I had the phone in an infinite loop of installation gears for a few moments and then phone rebooted. I tried several times to do hard reset and nothing worked. I tried to use the windows phone recovery tool, but it couldnt detect my phone. In much frustration I just started pushing each button in turn on the phone to see if I could fluke some form of rest. Initially nothing worked until I finally got the Lightening bolt and gear icon. Thats when I found this thread.
I read the entire post and tried everything there, I still couldnt get my phone to work. So in desperation I tried the Windows Phone Recovery tool again and this time when it said that it couldnt detect my phone, I clicked on the link for "cant detect phone" and selected Nokia Lumia (I know this is the HTC thread, but this information might still apply). It still said that it couldnt find my phone, so I did a hard reset (volume down and power until vibrate and then release power and keep holding volume down). Then the Lightening bolt and gear icon were replaced with large NOKIA logo on the phone and the recovery software could detect my phone and allowed me to reinstall Windows Phone 8. So now my phone is working again and I am going through the process of upgrading to 8.1 and then I might try the Preview upgrade again