You can back up your HD DVD using various methods. if you want full 1080Presolution and playback on Ps3 or other Blu ray players i suggest AVCHD format using DVD DL. if you are happy with 720P then you can convert to a single layer DVD.
You can back up to blu ray if you want but its not necessary or economical.
I would not buy a HD DVD burner as the format is dead.If you dont know this then encoding 1080P video is prob beyond your IT skills.
What is your intended playback method????
Have you read the guide suggested by Jo?????
Like i said before more info please then you will get a directed response!
I dont mean to be rude because i would like to help you but you must understand that there are many back up methods. If i knew what you wanted to do then i could help.