As a Mac user, I find this array of different Windows versions with different possibilities and different EULA's bewildering, not to mention that you will be only able to install a copy twice. One problem is that you never know what to expect when you sit behind a Windows XP-machine. On some machines it is possible to have some rudimentary version of fast user switching, while on others you have to leave close everything before another user can log-in. I suppose that with Vista the confusion will only get bigger as it looks like there are more different versions.