My Imac is eating up memory. I have in total a 250GB harddrive. It is now full. There is no way I have used up all this memory myself. 2 months ago I still had 200 GBs free space, so I dont understand where all this space has dissapeared to. I deleted a few movies etc to free up some space, within 2 hours another quarter of a GB had dissapeared even though I wasn't near my computer. Has anyone any idea what could be going on?