That link applies to Windows XP, not Windows 7. It's not relevant to this thread.
I agree with all the above comments about not using DVDs for backups (that does kinda start getting expensive soon with how many discs you need anyway).
But I understand the OP's desire to use different kinds of backup media.
I suggest that you use a large-capacity USB stick in addition to the external HD drive, instead of DVD media. This is a very durable backup solution and much more convenient than a set of multiple discs, and it's the method I use personally.