itunes backup won't work, error 4020

I have a new computer with Windows Vista. I reloaded all my music on itunes and put some new stuff on it and now I want to do a total backup. it tells me I will need 3 DVD's, goes throught all the motions, then tells me the burn failed, error number 4020. I have tried 3 times and the DVD's are all blank. How can I get this to backup?
Thanks Jerry