On the eve of the MacWorld keynote, I thought it would be appropriate to highlight the single application which enabled me to complete my "switch" from a PC to a Mac: Parallels . For those who may not know, Parallels is a virtualization environment for the Intel Macs. It enables you to run an operating system - from Windows to Linux to DOS - within Mac OS X. The entire guest operating system is stored in a single file, which can easily be backed up and/or moved around easily. I first saw Parallels at a client, where Ben Rudolph from the Parallels team was getting ready to demo it. He turned on his MacBook Pro, fired up Parallels, and then stared up a pre-release version of Vista. He looked at me and said, "Pretty cool, eh?" My only reply was "Why?" He chuckled, but went on to claim that even a pre-release version of Vista worked with their software. From a tecnical point of view, it was quite impressive, as having Vista gives you access to all of it