You should format your ipod for your home computer, or whichever machine you're going to want to dump your music onto when you want a cange of pace. You can set your ipod to manual as described above, and that way you will still be able to get files off your computer at work (mac) but will not be able to update ipod software, or take files off the ipod and put them onto the mac. ipod will not "reject" being plugged into a mac once it's been formatted for windows, it just wont be compatible for updates, and if it's configured from the home computer to recieve ANY automatic updates, you may experience problems. There are a couple good third party programs out there, built mainly for recovering itunes library from ipods when a user changes computers, but I wouldnt reccomend using them to maintain identical itunes libraries at home and at the office. You can find what you are looking for by just searching for the action you want the program to perform.