Batch renaming in Windows XP

I have over 9000 music files from ocremix.org but I hate how they name their files. It's always:" "game_title"_"songs's_title"_OC_ReMix.mp3 . Such as:

Metroid_Prime_3_Yellow_Valkyrie_OC_ReMix.mp3
Super_Mario_Kart_Trippin_On_Rainbows_OC_ReMix.mp3
Super_Metroid_Mother_Brain_Suite_OC_ReMix.mp3
Super_Metroid_Zebes_Rising_OC_ReMix.mp3

I'd like to rename them all to "song's_title".mp3 without it taking a whole day. How does I do that?

please tell me you don't sit around listening to the super mario theme on your ipod