id say no more than 120gb. even if you have all of the most popular steam games, then battlefield games, a few racing games, then extras (flash, browsers, adobe air, other rubbish) you arent going to take up anywhere near 100gb. but its best to be safe. i was going to say even if you had WoW, but then again thats on mac and whether you have the discs or not you can still install it on mac since you just download the blizzard installer