Some versions of Windows (Vista is the main culprit I think) sometimes lose the CDROM, usually blaming some new installed software, personally I think it is just a random Windows thing.
If the drive is working out of windows e.g. able to boot a windows or linux disc then it could be a registry problem. If so, try googling along the lines of Windows cdrom hi lo filter.
Touch wood it is just the filter thing and is a no cost option