Drive On Mac Pro Won't Open For Firmware Restoration?

Hi--

My Mac Pro (early 2008 model, OS 10.6.8) has recently begun having problems that seem firmware-related. When put in "Sleep" mode overnight, it wakes up on its own after about two hours of sleep and remains awake. Also, from time to time it will display the prompt window ("Do You Want To Shut Down?") for a hard (button) shutdown---without the button having been pressed. Resetting the SMC and the PRAM solves the problem for awhile, but it's becoming necessary to do that more and more frequently---at first, the problem occured about every six months, then weekly, until now I'm getting the shutdown prompt and have to reset the SMC almost every day.

Internet searches of this and other forums have indicated that a possible solution is restoring the firmware. I have made a Firmware Restoration CD but I cannot get the machine to recognize it. That is, when I press and hold the startup button I get the "three long-three short-three-long" beeps; according to Apple's FAQ on ths subject, the optical drive door should then open and allow me to insert the Firmware Restoration disk, but that doesn't happen--the computer just goes right on with the normal startup sequence.

Please advise.