Dvd burner fails to find disc

I am a newby.
I recently bought some dvd’s back from Bali I have been able to make back up copies of most of them but I have a couple which when put into my dvd drive seem to be invisble as the drive is shown as being empty in all my copy programs and is not even shown on “My Computer”.
These dvd’s play without any hassles on my stand alone dvd players it is only in the computer drives that I have a problem :a

I guess none of you can help me as there has been no reply of any kind .
thanks anyway