Acer recovery dvd type



Trying to do a back up for my new Acer Veriton M498G-Ui5650C:3.2Ghtz Core i5 4GB Ram 500 HD Pc.It sounds so easy but..when I put the dvd in, when prompted, I get an unsupported disc format error. I am trying to use a DVD+R Dual layer 8.5 G disc.
My only thought on this, was the possibility that they don't want me to use a Rewritable disc because it will have Windows 7 on it. any other feedback out there? I have no back up disks for this PC at all and it isn't letting me make them. I'm reading about some of the recovery issues and wondering if I made the right decision buying this PC.