I have found if you tend to buy or download a lot of new software, most of it starts at 10.3 support as the earliest. But if you plan to only have this for a short time, don't waste your money, save up for a better Mac Mini, which, if you wait until june, will have the newest OS X 10.5 (Leopard), otherwise, if you buy one before then, you will get 10.4 (Tiger), which is still the world's most advanced OS .