If you play a game which uses one particular version of that library, then that game will attempt to look for it on your system. If it cannot find it, then it will tell you. If you keep re-installing it also, then that should not be a problem, but that is not your question. The question seems to be testing the logic that the newer 2010 library will have the same functions as the 2005 library, and that the game or software will attempt to use the newer functions. The truth is, it is possible for someone to write a piece of software which will be able to auto-detect what libraries are on your system and make use of whatever functions it needs. So the answer is: that it depends on how they wrote game. You could always uninstall one version and see what happens.