DVD not recognised by dvd burner tools

I have a HP NC6400 with a DVD RW multi recorder.
I am trying to burn some dvds for back-ups matters but no matter the dvd burnner tool I use (InfraRecorder, Furn4Free, Express Burn, etc) I always get a message that in general says that No Recorders Available or any other message of the same sort.
It is strange but it happens only when I try to burn a DVD. I can burn CDs without problem.

The driver installed on my laptop is Matshita a765 and I am using Windows2k.

Please, help me!!!