Will it read some DVDs and not others, or is there one particular disc it won't play? What type of DVD are you trying to play: data, video, pressed, recordable, etc?
If your LTD-163 is out of warranty like mine, then you are running out of options. DVD-ROM drives use dual laser pickups because DVD's and CD(R)'s operate at different laser frequencies. It's possible that the DVD optic section has failed, but if not sometimes cleaning a drive will restore it to full function.
I assume U know u must use a software ( WinDVD , PowerDVD etc .... ) to read DVD movies . What are the errors messages ?
Also i assume you have enabled DMA on your drive .