How do I copy a movie on to a blank DVD?

In order to copy a DVD movie to a blank one, you can copy the files from the DVD on your computer's hard disk. Insert the DVD you want to copy and open the drive. Select the files you need and the location where you want to save them, then click on copy. Then you can insert the blank DVD and burn the disk with Windows Media Player. Follow the steps provided by Microsoft and read the burning tips if you have Windows 7 in order to successfully create a high quality DVD. 

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Source:
http://answers.microsoft.com/en-us/windows/forum/windows_7-pictures/how-do-i-copy-a-dvd-movie-on-to-a-blanck-dvd/cac586b4-ec2c-491d-bbbd-3e3bf6b56043

You may follow the steps below -

1. Insert the DVD in the CD\DVD drive.
2. Open computer, click on DVD drive, and Select the files you want to copy. To select all files, press Ctrl and A keys together, to select files randomly press Ctrl and left mouse click on the file.
3. Right click on the selected files, click on copy.
4. Select the location where you want to save those files, right click and paste it.

Then you may insert the blank DVD drive and burn the disk using the Windows Media Player. You may refer to the below link for assistance in burning the DVD and other details