I've created a bootable memory stick on a Windows computer, and tested it on an HP PC. It's made from a 64-bit image of Ubuntu 11.10, downloaded from http://www.ubuntu.com/download/ubuntu/download. When I boot from this memory stick, there is some kind of boot menu, where I can choose to run Ubuntu from the memory stick, or install. I select Run from memory stick. (the words may be wrong here, I'm taking it from memory.) From this point, the screen is black (but backlighted), and I can't do anything but turn off the computer. It gets hot, too.
Has anyone been more successful than me? Are there known issues?
The computer is a 15 inch MacBook Pro 5,1 (unibody, late 2008), 4 GB memory.