Innotek's GPL-licensed Virtualbox software lets you create a virtual operating environment inside your PC's real operating system. I've been using Virtualbox for several months now on a 32-bit laptop running Ubuntu 7.04, and I've been impressed with the software. However, my main PC at home utilizes a 64-bit version of Ubuntu 7.04 Feisty Fawn, and Virtualbox didn't support 64-bit OSes -- until this month. Now that I've tried it, I'm happy to report it works just as well as its 32-bit sibling.