Check condition, medium not present means the drive isn't recognizing that you have a blank cd in the tray.
Have you changed anything lately? Different type of cds perhaps?
Tell us the make and model burner you are using. Can you burn anything else, like data to a cd or dvd?
You can try the Microsoft Fix It tool. There is a link in my signature below that says Microsoft support for optical drives. Click on it and follow their instructions.
If that doesn't work, you can try removing upper and lower filters: http://pcsupport.about.com/od/driverssupport/ht/upperfilters-lowerfilters.htm