Boot from a flash card or USB flash stick ...
With my Linux operating systems on my notebooks & netbooks , I can boot very quickly from flash memoory. It is much faster than CD or DVD.
Depending on which boot I choose, I can have my computer as an Apple Mac OS-X ("Hackintosh"), Windows XP, Win7, or even Linux. These can be the real, commercial products, or the work-alike imitations. Generally, if is 'buntu-based, it is quicker, less-power hungry, and less buggy than the "real" operating system.
If I want an exotic program, like the latest version of Dragon Naturally Speaking, I generally need to use the real genuine operating system. So I prefer Kubuntu 12.04 at the moment, with all my data stored in a genuine Win7-NTFS partition. All my operating systems can access all my data: words, pictures, audio & video.