Sharful wants to copy some DVDs, but they contain more information than will fit on his blank discs.
DVDs can be manufactured with either one or two data layers. Single-layer discs hold 4.7GB, and are also known as DVD-5s. Double-layer discs hold 8.5GB, and are thus called DVD-9s. (Why do I suspect someone in PR came up with those names?)
The vast majority of stamped DVDs--those you buy with movies and TV shows already on them--are DVD-9s. You can usually, but not always, recognize them by their gold-colored data side (the side without the label). But most blank discs are single-layer DVD-5s.
You can burn double-layer discs, but it will cost you. You might even have to upgrade your hardware, as not all DVD drives can write to dual-layer media. Check your drive's documentation to see if it supports Dual Layer or DL media.
The discs also cost more. Checking Best Buy's web site as I write this, I find a 25-pack of DVD+R's selling for $10, and a 5-pack of DVD+R DL discs for $20.
By the way, stamped DVD's can also be double-sided as well as double-layered. That means the studios can release movies on DVD-10s (a single layer on each side), DVD-14s (a single layer on one side; a double on the other), and DVD-18s (two layers per side). They rarely do, however, probably because people will pay more for a two-disc set than for a single disc--especially an ugly single disc with no place for a label.
Visit http://forums.pcworld.com/message/149119 for the original forum discussion.