This is strange, but it's exactly what happened yesterday:
I've got a PowerBook G4, 2GB RAM, running OS 10.5.7, with all additional Apple updates current. The DVD/CD drives functioned nominally. I had just burned a DVD on Monday (today is Thursday). I had had Toast Titanium installed for a few months, and decided to go for Toast 10 Pro. Following the upgrade directions from Roxio, I deleted the existing Toast-Ti app, rebooted, then downloaded and installed Toast 10 again, followed by all the good stuff that comes with the Pro package. No error messages during installation, and Toast Titanium resides in the Toast folder as a 676.9MB icon. So, I launch Toast Ti....... and it does not appear. Oh, Command-Tab shows it is an active app, but it's not there. Curious about this, I try to pop in a blank DVD, thinking it might bring Toast to life, but the DRIVE ITSELF DOESN'T WORK. It doesn't whir or grab the disk, or nothing. So I try a commercial movie DVD: same thing. A disk cannot be inserted. Under the Apple menu I went to "About this Mac" and looked at the hardware details. For "Disk Burning" I get this message: "No burning device was found. If you are using an external device please make sure that it is connected and powered properly."
Is this just coincidence? Is it likely that my disk drive died, or did I do something with the software that caused the disk drive to become invisible to the rest of the OS?