Thanks, Navy - I'll get the Win10 KYHI disk and see what happens.

I see KYHI's tools are Win10/Win8.1 - will either of those work on Win7 as that is what is currently on the machine, although as I mentioned, I can't boot into it due to the corrupt compbatt.sys....

CountMike - I was unable to do a Repair Installation of Win7 because the dvd I have is the original Win7, and Dad's is fully up to data, so not the same version of Win7.

Slarty - I tried SFC, even...

My Dad's laptop running Windows 7 crashed the other day, and after running Startup Repair, it found that compbatt.sys was corrupt. I tried copying over a good version from my pc & recovery partition...