Prolly all that modding. If you mod with games other than dwarf fortress, doom, etc. etc. For example, I got bored of skyrim (ran out of gameplay) and deleted it along with all the mods I had. Freed up close to a hundred or so GB of space. I remember on my old laptop, I had about 48GB in mods for oblivion and around 10 to 15GB in morrowind mods. Another between 30 and 50 GB in FO3 mods and a measly 15GB or so in FO:NV. Bethesda games are massive space hogs when full of mods. I like to think that mod folder size is directly proportional to how good a Bethesda game is. The larger that folder is, the worse the game is. It should be noted that most of the mentioned games were played and beaten before mods were installed. The exception is skyrim, which I installed mods to before completing the game. Those mods being unofficial patches and fixes. Can't wait for skywind, looks like it will be nice.