Media player meltdown in Vista

I have a computer which is just over 6 mos old, and it came pre-loaded with Vista basic. Other than me stupidly not ordering extra RAM, I love the system (which was a pre-built system from 3-B Tech.net computer store).

Recently ,however, my sysstem stopped playing Windows Media Player files. If I attempt to play an audio cd, or watch a streaming video online that is not RealPlayer or Flash or QuickTime, it will not work. I can't even open Media player, even though the directory still shows it. When I try to open WMP, I get a breif "hourglass" thing, then nothing. It will not open!

I tried to go to Microsoft Update and download the "latest version" of WMP, but the latest version there gives me the message "The version currently installed on your system is more current than this one, therefore you cannot install or update with this version of WMP" (a little paraphrased, but basically , yeah).

What can I possibly do? I hate to have to do a full re-install, for fear of it never being the same. ANd BTW, this began well before I upgraded the RAM.\

Thanks for any help in advance,

Scratching My Head in TX.

EDIT: Sound works fine otherwise, whether on videos it will play (flash, etc) , or Yahoo radio, or WoW sound effects.....