Huh, I just installed Ubuntu 11.04, dual boot, on my Vista 64bit machine. It was easy using a downloaded and burned Ubuntu image and the directions at the Illustrated dual boot site
. There are a number of ways to go about it, as described at the website.
I am really liking Ubuntu these days. I installed it on one of my old notebook computers and was so impressed that I decided to dual boot my current desktop machine.
Depending on the size of the hard disk you intend to install Linux on, I suggest about 15GB for "/" (the boot or OS partition), about 2GB for the swap partition and the remainder for a "/home" partition. That allows you to format the "/" partition and reinstall Ubuntu (not sure if it works with Debian) without losing your bookmarks and settings.