Open your Task Scheduler and choose
create basic task
Give the task a name and description and push next
For Trigger choose the option that suits your needs (this one should be self explanitory) Daily at 8:00 AM for example.
For action choose "Start a Program" and choose your MP3 file you want to wake up to
Finish the task.
Test it by running it manually.
I would recommend using Windows Media Player as your default media player to enable it to open when the .MP3 is called. I am unsure if iTunes will play the song as soon as you open it. I can confirm Window Media Player did as I just did a test myself.