Take a deep breath. Calm down.
Here's what we're going to do - save all your personal settings and reinstall ubuntu from scratch.
Now go find or burn a copy of ubuntu, 12.10 will do, or 12.04, and a USB drive. Boot into it.
Now you have a working linux install from the livecd(I hope!), and you will need to open the drive with your old install of linux. This should be automounted, if not, comment and I will edit to tell you how to access it.
You need to copy the contents of /home from the old install (this should show up as a drive or drives in the livecd)- Copy everything as this contains any settings specific to your install, and a good chunk of your personal preferences. Upload what you want to, now. Copy anything else you need. Ideally you'd also want to retrieve a list of what additional stuff you have installed, but I can't remember how to do that off hand from another install. If you can't read /home, it gets tricky, and you'd selected an encrypted partition. There's probably a way to access it, but that might need you to boot into the old install, and use the command line.
Now comes the slightly scary part. Its too much work to fix a borked upgrade. Wipe and reinstall those linux partitions as per normal, with the same usernames. Copy /home back in place (i'd probably leave out anything specific to unity, or if I REALLY wanted to play it save probably copy just the desktop folder and some directories starting with a . - these are hidden directories with program specific files). Boot into the new install and install whatever packages you need.