I am running Windows 7 64bit on a Dell desktop machine. Mysteriously, my DVD drive disappeared from Windows 7, and going through the hardware manager to re-install it did not work.
It turns out that iTunes (effing Apple! "it just works", hah!) puts in an ASPI driver from Gear Software.
To get my DVD drive back, I followed the instructions in this Microsoft KB article. It involves going into the registry using Regedit (don't forget to do it "run as Administrator") and deleting the UpperFilters key, which to the GearASPI file.
Problem is, if you update iTunes, you will have to do this again (I did).
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