no disc in drive.is this when you try to play any dvd or just one particular dvd?maybe your dvdrom drive is starting to age.or maybe a clean of the lazer might help.
are there any errors reported in start/control panel/performance and maintenance/administrative tools/event viewer
look under the system or application tabs? something like "dvd has a bad block" etc? could mean a duff drive or damaged dvd disc.
what version of powerdvd do you have?
patches click here may help?