What they dont commonly let you know with DVD-writable discs is that they work slightly different from normal CD-R's.
In order to get a DVD-writeable to work in your computer, first you have to prepare the discs.
The reason the term burning is used in the industry stems from this preparation procedure, which used to be common with the first CDs but now CD technology has started being sold pre-prepared, however dvd's are a new technology the suppliers have not got the facilities to pre-prepare them yet.
This simple procedure does not take long and you can do it to all your blank disks to get them ready for use.
simply get a strong heat source, a cigarette lighter will do nicely, and hold it beneath the new dvd moving in small circular movements covering the face of the disc. Hold the lighter about 4 inches below the disc wilst doing this, and you may want to hold the disc in some tongs so you dont hurt yourself.
Now the desired effect you are looking for is a deposit of black soot on the surface of the disc, this helps activate the chemicals used to store your data on.
If you feel confident, apply the heat for a little longer so that the disc slightly melts on the surface and maybe bubbles. this is somethign the pros do to get more capacity out of the discs as the bubbles act as tiny "lenses" that magnify (compress) your data.
A properly prepared disc will upon insertion to the drive be detected by your operating system, and a wizard will come up guiding you through the DVD burning process.
If this does not work and you are using windows 2000/windows XP, then delete the file in the root of your C drive called ntldr, as it is a junk file commonly known to block DVD burning.
hope this is helpful, despite many harsh replies you have had here.
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