Sound muting program for Windows?

Sometimes when I go to sleep I leave the computer playing some music, but I'd like to tell it, once X minutes have passed just mute the volume.

Does anyone know of a program to do so? I'm targeting Windows 7 here but I guess one for Vista will do equally.

Personally I'd do this using AutoHotKey to pause my player. Just add a script like this:

^Pause:: ;Activates with Ctrl+Pause, you may want to change this
  Sleep, [time in ms] ; Replace [time in ms] with however long you want it to wait before stopping your music
  Send Pause ; my music player pauses when i hit the "pause" key, so I'd use this, if yours doesn't, try Media_Stop or if you really want to mute, use Volume_Mute

EDIT: just saw this on lifehacker and couldn't help but think of this post, so I'm adding it http://lifehacker.com/5522204/itunes-sleep-timer-stops-playback-after-a-user+defined-time