Wait, overclock your CPU for vanilla World of Warcraft? What is it a Pentium III processor? Check out your background processes and see if you got something hanging up. Granted, it could be World of Warcraft hanging up, but I would suspect it is because of something going on behind the scenes (another process hanging up your CPU). Considering the fact that vanilla World of Warcraft can run on an 800MHz processor See Here & 256Mb of RAM. I can guarantee you unless you are playing on a relic of a computer circa 2002 that your processor isn't the answer. With all of that being said, World of Warcraft does use a fair amount of disk I/O (which in turn can cause lag if a lot of textures, models, etc are being loaded) which can cause lag and other artifacts. Check your processes, see what's going on there, then I would investigate your actual hard drive if the problem makes your game unplayable.