Meh, personally I prefer to install an OS properly than to try and use a removable version (such a Live CDs with Linux). I never have more than one OS on a computer at a time, simply because I'm not a great fan of the way in which they do things differently. Sure, they'll probably work fine, but anyway...Ideally, I get a full OS (namely not DSL) and have it on my computer straight after a format. I like to keep it tidy, so knowing that I don't have lots of little files that might intefere with each other (even if they don't intend to) isn't a nice thought.