I have a feeling that reinstalling Windows wouldn't solve the problem of the missing Media Drivers.  Do you want any other media players other than DVD ones?  Windows Media Player can play DVD's if you really feel the need to.  I don't like it very much, but that is my opinion.  I have an older computer, so I really don't have a need for a DVD program, but the computer store installed it on there anyways.  This program in question is WinDVD4.  I don't know where you can get it, and if it is free or not, but it is better than the open source alternatives.  It usually comes with the newer XP versions of computers, and on newer, non-Vista laptops.  I don't know if it comes with Vista, and I will not hazard a guess.  So, summing up a really long post in a sentence, search for WinDVD4.  Also, it may depend on which Windows version you installed.