A friend has a P300 (Vista Home Premium) with a  DS8A4S slimline DVD drive. It plays commercial audio CDs just fine, but does not recognise DVDs at all. By that I mean that when a DVD is put in the drive, it does not show up at all - select the drive and the message comes up "please insert a disc into drive D". Also, when I put a a CD full of MP3s that I'd burned into the drive, "Properties" reported that the disc was empty, when on my own machine (Win7 Pro 64), it correctly shows as full. I also tried a commercially produced MP3 disc, one I bought from Amazon.com, and it played just fine.  There are no warnings in Device Manager, selecting Driver Update brings up a message that the driver is already up to date.  I was thinking that perhaps it's not a mechanical issue, since it does read and play some discs. Any suggestions will be very gratefully received. Thanks!