Disc is-write protected

Hello,

I've joined your forum today hoping that someone will at least reply to my question as I'm not getting any help from other forums

I've been backing up my files using a DVD-RW disc for years.
Today I had my monthly prompt to insert disc for another back-up.

Now this is where I am having a problem - for some reason I'm getting a warning triangle saying "Disc is write protected"
I've tried putting in a new dvd disc - Clicked to format then a pop-up appearers saying "Format was not successful
CD Drive(D)
The disc is write protected "

I've even tried to go it alone and burn files to disc but the same message comes up when trying to format.

Can anyone advice me ( not technical wording please) in what I should do next?
My laptop is a Windows Vista Home Premium

P.S. I don't know if this has anything to do with it , but... I can play cds without any problem, as for play dvds it doesn't work?

I've checked Control panel- Autoplay and the following has been applied....
Audoi CD - using Windows Media player
DVD movie - Media player
Enhanced DVD movie - Media player
Video CD - Media played
Have I tweaked this wrong if so please advise