One day, out of the blue, my wife's CD Drives disappeared from Windows Explorer without warning and little trace. Device Manager shows them both with Code 39 warnings. One is an LG GGW-H20L BD Burner Drive and the other a Pioneer BDC-202 BD-ROM Drive and the OS is Vista.
So far I have tried unplugging/re-plugging the cables, uninstalling/re-installing the drivers and downloading new drivers. Windows says it already has the latest drivers. The LG and Pioneer websites don't seem to have downloadable drivers specific to these drives.