I did this for a while with my stereo. It costs nothing... as long as you have a computer is in the same room as your stereo.
All you do is hook up your PC to your preamp with an analog cable. Assuming you're running windows, go to Control Panel > Scheduled Tasks. Here you can set specific times/days to launch certain applications. I assigned the generic program "cdplayer", a windows application, a time to launch every day (you can also specify which days to launch).
There is an option in cdplayer that plays a disc automatically when the program is opened. This must be enabled for the "alarm" to work.