Well, while the size of the program directory does have something to do with the complexity of it, but how much of that disk space is taken up by media versus code that does honest-to-goodness computation? Most of the space under Windows is going to be taken up by all the program executables that make up Windows, Most of the space taken up under WoW is going to be the media files that really have nothing at all to do with the functioning of the game. Sure, you could have graphics glitches, but that often isn't caused by a corrupted media file, but by the code improperly using the media file. The media under WoW is just the presentation, the important part is really your control input going down the wire to the server, the computation that happens there, and then the update info that is sent back. I'd hazard a guess that about 80% of those bugs have very little to do with the client program, or if they did, that they required some massive fix on the server end and a relatively minor tweak on the client end.