Question Author
Right, now for a response to your welcome suggestions.
Ivor: It's a brand new PC with a DVD recorder and as far as I'm aware the dics I have are one sided (8.5GB 8xSpeed 240 mins)
Stoofur: I'm trying to burn a 1935 B&W film that I've got in my Realplayer library; duration 2hrs 30 mins. So I expect it's not HD.
OG: Yes, the double layer disc is 8.5GB and my new PC didn't have a manual for the DVD drive so I can't answer your question.
Fender: I downloaded this programme but it turned out to be a trial version, which I'm wary of, and it seemed too complicated for my limited ability.
I know how to burn a CD from Realplayer and thought I could just insert this double layer disc and burn as usual, but it's proving a pain ! Anyway, thank you all for your help.
D