If you haven't found this already you want to visit:
I finally got CHKDSK to run on reboot. How to troubleshoot the problem.
It was a revelation. I was just checking to find the log described when I spotted 'elrawdsk.log' on root. So I carried out the registry procedure of disabling elrawdsk.sys from loading and... voila.
You may not be as lucky but there's a procedure described that ultimately will bring a successful solution to your chkdsk woes.