Well PC is slow anyway... just reading stuff over won't help. Try to summarize all that you need to study and physically write it out: The act of writing it up helps and gives you a more concrete goal to just "studying." Say if you're studying history... then make it a goal to condense everything to, for example, 2 pages only. When you think about how to shorten things (regardless of how much actual material there is), you are actively engaging the material and is therefore, studying.