writable DVD speeds

Friends,
I have a Dell XPS 8100, 64-bit OS with the following DVD/CD-ROM drives: HL-DT-ST DVD+-RW GH50N; PLDS DVDRWBD DH-6E2S. I want to use a software program out of Dell to burn backup discs. How do I make sure I have the correct write speed, i.e., 4x, 8x, 16x? Is there a compatibility with Win7 Home Premium and a specific speed? I am looking at Verbatim over some of the other brands and feel a small package will do as I have very little important info to backup, yet I wish to use good quality hardware. I thank any and all in advance for sharing info regarding my query, and I do remain
Most cordially,
Chen

Normally when you insert a disck to burn it will go to it's default maximum that the device can handle, however in that box that shows the speed you can usually click on the pointer on the side and select a slower speed if you wish.
There is no 'correct' speed as such however the slower the better if you have patience. Slower means less chance of errors.