I have enough problems with my system that it might be corrupt - in more
than one place. This is just a guess. However, I have over 100 apps
installed and would hate to have to reinstall all of them with their
specific settings.
1. How can I tell if my system IS corrupt?
2. If it is, what is the EASIEST way to get back to where I was before
it became corrupt?
3. Is there a way to un-corrupt my system without reformatting and
reinstalling the OS?

I've been very careful to install only legitimate software and I've
faithfully run anti-malware programs and Norton Internet Security. I
also have backups of my whole system. I'm hoping that there's some way
to determine what my problems are and fix them without a fresh install.
After all, if a system can become corrupt this simply, what good is it -
especially if it can't tell me what's wrong and what needs to be fixed?