You certainly couldn't eject the clients cd drive through asp (although you may be able to eject the servers cdrom (tho never tried it). You're only option would be client-side, i presume, because i.e is 'sandboxed' you wouldn't be able to access things like the cdrom drive, although that isn't definate.
Response.Write "Please press the button on the front of your CD Rom drive NOW!"<BR><BR>Seriously though, if it could be done, it would just be plain irritating. Your users will dislike you for interrupting their music/the program they are installing etc.