Ok it sounds like SOME retail(movies from the store) dvd's work and others do not. This can be caused by a bad drive.
If this is the case, I have seen some drives stop reading dual layer discs(A DVD can be made of a single layers or dual layer. Dual layer gives the disc more space, but a broken drive may not be able to read it). If this happens only single layer discs will still work while dual layer will look empty as windows things there is not disc in the drive.
It shows an empty drive for Windows built in burning feature.
Check and see if all your working DVD's are in the 4 to 4.4GB range. If you find nothing larger(6Gigs and up) chances are the drive is not functioning correctly.
Single Layer disc 4.43GB
Dual Layer 7.33GB. Yes almost ALL kids movies(Disney and Dreamworks) use dual layers discs and have FAR better image quality.
It is kind of technical, but a drive has to refocus(it you run an open drive you will see a large(bigger then the red laser point) red light used when the drive is reading the second layer) to see the second layer. When that part breaks, the drive no longer reads dual layer discs but reads single layer and cd's fine.