Hi Tony!
I back up to DVDs and CDs. It is easier. It's been a few years since I needed an external HD. There's way too much hardware in my office to bother with extra drives. I need elbow space!!!
Now, as most wise ones I only back up the files that I've created and downloaded. Basically everything but the OS, the drivers and the programs. I only back-up system and programs when I'm sure that it all works fine. In your case (considering the damage to the OS) just stick to backing up the files that you've created yourself.
IT will be impossible to sort through all the programs , drivers and system files in order to find out which ones work and wich ones have gone bye-bye.
But I'm glad you have things under control. As easy as it may sound re-installing OS and programs is a rather time consuming process. It is always good to find somebody else to do it for you.
-ED-