re-installing system

[Billie Walsh]

This was a clean install of 18.04 on an HP laptop, quad core AMD 8 gigs 
ram.

I suspect something went wrong during installation. Nothing will install 
from the repositories. It comes back with an error that says I need a 
"gtk3" something. Googling is no help or anything else I've tried.

I'm wondering if there is something that will re-install everything from 
a dvd or...................... that doesn't mean wiping the hard drive 
clean and starting over. I'm not against doing that but would rather not 
if I can. Everything that I wouldn't want to lose is on the second, 
Windows, hard drive [ yes, it has two hard drives ].

I guess what I'm thinking is a complete install without removing what is 
already there, just overwriting, and hopefully install what that GTK3 
gidgit is.