backup does not like dvd-rw ?

[geordiejohn]

hello i have got an apple minimac 80 gb with leopard 10.5.6 and when i try to run personal backup with a verbatim dvd-rw it keeps saying install a blank dvd which it is,do you think i need to buy a dvd+rw dvd ?
thank you.

 

[alphaod]

Did you erase the DVD-RW before you tried to use it?

 

[geordiejohn]

it would not let me erase it