WMP should be a 'windows component', which you reach by control panel > add/remove programs >add/remove windows components. There shold be a list of items including WMP. Put ac heck mark against it, save and reboot. That will return the version which was under the original windows installation.
the other nite i upgraded to wmp10,i had wmp9. i did not think after downloading that i would like it as well,esp. the radio tuner station feature. i had a few saved that i could not find on wmp10. so i did a system restore but #9 was no longer there nor was 10. i tried to download 9 off of download.com but got a message stating something about it no longer availible, can,t remember exact reply. i run windows xp sp2. i did download wmp10 again, any way that i can get 9 back??? thanks

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic