ITunes forgets library, loses previous ones and won't rename files

Question

Ok so had it up to here with some unimaginably bad software design in the last couple of weeks.
Order of issues: I updated iTunes, which is now on 10.1.0.56 (btw I can't get it to update to iTunes 11 as it says that the server cannot be contacted).
On reopening iTunes my library had disappeared. I searched online, found all the stuff about bringing in your previous iTunes library, except there is no folder named 'Previous iTunes libraries' in my iTunes folder. Also, I am aware that the issue may have been caused by AVG, which I have now updated so hopefully that will prevent it happening again.
So I just imported all the files into iTunes again, hoping that it will have updated all the tags for the 60gb+ worth of music, and would just put all that info back.
Instead, it turns out a whole load of music is incorrectly named, failing to pick up folder tags which are actually attached to the files (example: 8 Springsteen albums compiled into 1 'unknown album' folder, despite the fact that the files themselves are all correctly tagged with the albums.)
Going into the file structure, I've noticed that all these files were moved out of their folders and into
So I selected said set of albums and asked iTunes to get the track info, but iTunes told me that it can't find information for songs not imported using iTunes - I'm pretty sure most of them were in fact imported using iTunes though. Even if they weren't, the tags are there, but iTunes won't read them.
So as I said I have about 60gb worth of music on this computer and it's now a mess - is there ANY way out of this which doesn't involve a few days of my life spent changing things in iTunes? I know the easy way would have been moving the previous library but seeing as this doesn't actually exist... Help!

Answer 1

To clarify, currently on the 2TB external drive are music and videos. I want to split them up and hopefully save some space - and maybe foresee problems in the future when I hit max capacity on the 1TB external, and think about a 4GB (not the best option I see at this time) or another 2 2TB drives.
Doesn't the Library file just save locations when iTunes closes down so everything should be OK? I mean, the prog can recognize everything, it just won't download to anything, even if I move from the external drive an older movie to the new drive, it refuses to "see" the movie so I can download it.