I've been running Ubuntu 12.04 for quite a while, but after installing Windows XP onto another partition, the MBR was overwritten, etc etc.
I downgraded 12.04 to 11.10 using a Live CD, but it still didn't work. Used
boot-repair then reinstalled 11.10, and I got GRUB back. Yes!
So, I booted Ubuntu, and found that I had no control over anything except the keyboard. The touchpad, USB mouse, disk drive, USB anything, wireless card, all gone. This naturally means that I can't get anything onto the hard drive without lots of shenanigans using the Live CD. I've got a Gateway W340UI.
Eager to get 12.04 back.