Your original Windows DVD contains a small boot image that's not part of the visible filesystem, but it's what makes the disc bootable.
If you simply copy all the files on the DVD and write them to a new disc, the boot sector will be missing.
While you can use whichever option your burning software offers you to create a bootable disc from scratch, it would be safer (and more straightforward) to simply make a 1:1 copy as jumanji explained.
If you make an .iso image of a bootable CD or DVD, that .iso will contain the boot image as well and reproduce another bootable disc when written back to a blank CD/DVD.