Been having this problem for a while. I bought a new DVD drive for my laptop to fix the problem, an Optiarc AD-5540A. The same thing happened, the new drive installed and was available for a while but then dissapeared.
After it dissapeared I used system restore to go back to when it was available and re-installed windows to see if this would fix it. The installation finished and not a DVD drive in sight, even when I switch the drives they aren't picked up by plug and play installation.
If anyone can help that would be great, if you want more info just ask. I would really appreciate some help on this matter, it's mind boggling.