First make an m3u list of the songs you want to use (an m3u list is a file that links to mp3 files on your HD, you can make these by saving your winamp playlist).
Next, go to start->All programs->Accessories->System Tools->Sceduled tasks.
Click on "add sceduled task" and a dialog box will open.
Click next, then browse and select the m3u file.
Click next, then daily (if you want it to wake you up daily), set the time and start date, click next. Fill in your password and click next. Last off, if you've set your PC to "fall asleep" check the advanced box and click finish. You will then get a screen with advanced settings, tell it to wake up the PC to perform this task and click ok.
If you don't let your pc fall asleep, just click finish.
Don't forget to leave your PC on and make sure you can actually hear it from your bedroom. :-)