Need to restore HDD to Finder. Can't install Canoscan n1220u. New to Mac

First, I accidentally dragged my HHD from Finder to the desktop, and poof, it's gone. How do I restore it?

Also, I have tried to install my Canoscan n1220u to no avail. I downloaded the OSX drivers from Canon, installed them, (don't know if I did it properly,) and it still doesn't recognize the scanner. I saw a recommendation on a forum for software from http://www.sane-project.org/ but can't figure out how to use it.

Finally, How do you remove applications/Drivers?

Thank you in advance,

r.