Desktop Boot and Lockup

I have a Pavilion Elite desktop model m 9500f purchased in 2009.  It came with Vista but had Windows 10 installed a few months ago.  Everything worked fine until it suddenly shut down while watching a movie.  It would not reboot.  Auto repair from a blue screen did not work.  It has a diagnostic program that reported things are working, including CPU, Memory and Hard Drive.  I was not able to get a detailed error code/explanation that I think would be available working from the command prompt on newer HP models.  A blue screen did tell me "unmountable boot volume".  I could not rebuild the boot configuration data from the command prompt.  When I entered bootrec /Fix Mbr, for example, it told me "the system cannot find the path specified".  When I typed in bootrec /Rebuild Bcd it told me  "total identified Windows installations: 0".  I tried to reinstall Windows 10 from the original Windows 10 USB.  The installation failed when a location/drive could not be identified for installation.

Somebody on another web site had a similar problem and was told he would have to rebuild the entire system partition.  That person was able to do a clean reinstall of the operating system and I guess avoided the problem.  I am wondering if I have to "rebuild a partition" (which is beyond my ability).  I am looking for possible solutions and help.