Problems with 15.10 Release

I recently reported a problem with not being able to log-in after installing Ubuntu 15.10. (I am currently using an old 12.04 DVD to use my computer). It just opens in the Terminal with request for my username & password (I wrongly thought that I had forgotten both) but now I now find that even with the correct username & password, that I then cannot exit the terminal!
I just get the "last login; day, date and time on tty1". Is there any way to get out of the terminal now and start using my computer again?

Also or either: Can I download 14.04 again without loosing my old documents?

I don't like 15.10, wish I'd never tried to upgrade now. I only have the Ubuntu Linux System now, having wiped Windows off years ago. I'm running the 32bit System on a Lenovo G575.

Any help is greatly apprechiated.

Richard