Personally, I would recommend installing Ubuntu 8.04 from
http://ubuntu.com/, partitioning your hdd for 10% win, 10% lin, 80% NTFS storage. Then, you can safely reinstall XP/Vista whenever you need, while all of you important stuff will be in the 80% NTFS partition. You could use Ubuntu for most of the normal stuff (Fx3, OO.org, Pidgin, yada yada are included by default -- lots of great apps available as well, like Amarok, Opera, CinePaint, Nexuiz (FPS), and if I'm not mistaken it's possible to run WoW and some EA games on it if you hack hard enough (though not
very hard.), and Windows for gaming/RMXP/coding.
But, that's just me; I'm redmondose-intolerant. YMMV.