Updated today (3/4) and now I can't boot.

[Şerban S.]

THANK YOU!  I had thought something similar to what you posted [...]

You're welcome! Glad to help, if I can!

What I did in the beginning was set up Windows on one HD, Linux Lite on another, and "My Documents" on a third, so they could be accessed by either OS.

OK, I see here a good thinking!
This is how you can backup, on an "as needed" base, instead of backing up the whole thing...

Did you have a chance to watch the videos I posted?

Yes, I did, this was something necessary to be able to figure out what was wrong.

[...]I just bought a new SSD, since it was only $20 for a 120 gb drive!  I can just install the new HD and add the latest version of Lite.

A great idea, 120 GB is enough for one installation. Best of all, you get a great speed!

Also - I have a power switch array installed in my computer that allows me to turn off power to each of the 3 HD's if I want to.
I wonder if I could Set up the boot order (ie: 1 WIN - 2 Linux - 3 etc) and if I turn off the power to 1 Win will it then boot to 2 Linux?

Never used something like that. Might work, so test it, and if it works, it's OK.
I can hardly see any danger in testing. Nothing changes, except that one drive looks like "has vanished".
If you set the OSes right (with GRUB on the OS' physical drive, as I explained previously), this should work fine.

Best Regards!