Thanks, mciahel, for the link to the MS support article. It fixed my similar problem. Some details which might be of use - I was using an Acer Aspire 9410-2028 with the Optiarc 7530A drive under Vista Home Premium. I had downloaded, installed and used InfraRecorder from the Ubuntu site and burned a CD of the Ubuntu install. Following the next time I rebooted, I could not access the DVD drive with anything, neither InfraRecorder, nor with the preinstalled NTI burner software. Device manager showed an error 39 unable to load driver, etc. I tried the usual things like unistalling and reinstaling the driver, trying to find a newer driver on the Acer support site (very disappointed with the Acer support site). Note, I did not, as the MS article suggests, uninstall any CD or DVD software before this problem showed up. In any case, the manual registry edit did bring back my DVD drive. Thanks again for the link.