I am suferring from the same problem like many others where my CD/DVD drive has suddenly disappeared. I have also tried to follow the microsoft steps to remove the upper and lower filters, but I couldnt find it anywhere listed in the regedit. Now I am out of guess here what am I suppose to do here and which windows update has cause this issue. I am not even able to use the System Restore function, because i remembered that previously when i did that it kept reinstalling the Windows Updates.
I was having a MSI motherboard with an AMD Athlon processor which was running on Windows Vista with LG SATA DVD writer. After that i upgraded to Windows Vista and now the DVD drive has stopped working. When I checked in Windows XP on other computer then it was working fine. I even talked to the microsoft tech support for 2-3 hours but there was no solution for same. Now after frustration I changed me whole system with an Asus motherboard and quad core processor and now the dvd writer is working fine like before. So my guess is that maybe the motherboard chipset is having some issues with Windows Vista.
You can try to install Tune Up Utilities software which comes for free trial for a period of 30 days and then use it to scan the dvd problem. It was able to fix my problem so hoping that it would solve the case for others too. Another thing that you shouldnt do is never to download all upgrades from microsoft. From a list of updates atleast 4 of them give problem depending on different machine. Always try to switch it off and then organize it in such a way that the download will start manually by asking for your permission.