"Unknown internal operating system error"

[Belinda Frick]

It's likely that your hard drive is damaged. You can
try re-indexing the file if it's a data file, but if
there is physical damage, you need to replace the
hard drive.

Run Scandisk to find out if there is physical damage.

If you get this message as a "pop-up" and not in the
log file you should check that there is enough disk space
available.