I’ve never bought a piece of software which was so useful than parallels. Parallels is an osx virtual machine which enables you to run an other OS in a separate window – like XP in one window, ubuntu in another and simply switching between them. No need to restart your mac – just make yourself two images of the OS you would like to run, and you can run nearly every program you like in there. I tried to play halflife in my windows home environment, but games wouldn’t work there yet, because of the on existing grapic-card drivers for my intel-based graphic card running in the macbook – but maybe that’ll change in the near future. What I find really astonishing is the quite good performance, though I only like to give windows about 800 MB RAM – it looks as if parallels really works with dynamic RAM adressing, because the RAM usage of my OSX changes with the usage I have when running windows apps, and not by just starting the software – this is really great ‚cause it leeds to a flawless working flow when e.g. developing websites and checking in different browsers.