It looks like lots of people are having a problem with disappearing optical drives in windows 7. I hope a real fix is found. What's frustrating for me is it's an intermittent. I've rebooted about 30 times since installing 7, and it breaks down like this:
50% of the time - no drive showing in explorer or device manager, drive isn't powered (but it's there in bios and works under XP)
20% of the time - windows explorer hangs, either when I try to look under my computer... or sometimes all by itself shortly after booting up.
15% of the time - drive shows up, but disappears the instant I try to explore the contents
10% of the time - drive shows up, and I can explore the contents of a disk. But after a few seconds it disappears. I even managed to get halfway through copying some files when the drive disappeared (giving me a copy error)
5% of the time - drive shows up as an unknown type of drive (not as a DVD/CD drive). Explorer won't show the drive capacity but gives it a drive letter. Disk manager doesn't give it a letter but shows 4GB of capacity.
So yeah, I tried all the usual fixes like the registry edit, the command line to disable signed driver checking, etc. The most promising fix seems like installing a new driver/firmware for the drive. But memorex's crappy site gives 404 not found errors when I click the links to download the drivers. I may end up having to buy a new drive.