I don't really know why it has started to lag as of lately, when my computer starts having issues. I usually run CCleaner and Defraggler and it helps a lot. If that still doesn't work, I just reformat. In addition, I use Game Booster 3.5 beta (i don't like the razr game booster) and this helps SOOO much especially for WoW. It disables unneeded services and programs when you're playing games in order to boost frame rates. Just an idea.