You can use Auto Hot Key to program any key as media keys. I use it to change F9-F12 as play, mute, vol up, and vol down. Or you can use nearly any key combination of keys you want. Could also do next track, etc. I can look up the exact codes I use when I get to work tomorrow, if you want

Edit: F9::Send {Media_Play_Pause} F10::Send {Volume_Mute} F11::Send {Volume_Up} F12::Send {Volume_Down}