I have been using Ubuntu 10.10 for a long time but they have stopped providing updates for it.
I am installing Ubuntu 12 on VirtualBox. Spent some time finding the CD I had made a few days ago but then realized that VirtualBox can install the .iso from a folder. Using all the default settings, my first problem was the message "this kernel requires the following features not present on the cpu pae". I found that I just had to enable this "pae" and all would be fine. But at the stage of the install, the settings button was grayed out. I powered off the virtual machine and then was able to access the settings button. It was in one of the tabs.
I do not want it to install updates because this is just a test. VirtualBox makes me nervous when it says "Erase disk and install Ubuntu". I have to be confident that they mean the virtual disk. I would prefer that this was written explicitly. The drive is called SCSI1 (0,0,0)(sda) 8.6 ATA VBOX HARDDISK.
Well, I proceeded, having confidence in the logic, and after an hour or so, I have Ubuntu 12 on virtual drive. Love the colors.