I've a dual boot system with XP and Ubuntu. (Grub 1.5) Ubuntu was originally installed from a CD and has its own partition on an external hard drive.
After an upgrade from 11.10 to 12.04 the 3.XX kernel let me log in, but then give me a black screen. The 2.XX kernel give me a workspace, but with a distorted aspect. (I had to play with the monitor settings to even get the system button to appear.) I tried 12.04 on a USB and it looked OK, but was so slow I would never use it. What is the best way to reinstall 12.04 or even 11.10?