Option Three in the system file checker tutorial outlines how to see and read the cbs.log and hopefully determine which file(s) and damaged or corrupt. It's a fairly involved and time consuming process. It may likely require the skills of an analyst who can decipher the log. I am not one of those people.
When I've been faced with a system file checker scan that can't finish, I've jumped straight to a Repair Install. A repair install will attempt to fix your currently installed Windows 7 and preserve your user accounts, data, programs, system drivers
etc. If successful you'll have to reinstall Windows Updates. The repair install takes about an hours and reinstalling the updates may take slightly longer. Repair Install