I'm not familiar with a program called Windows 7 DVD Writer. Perhaps you mean Windows DVD Maker?
DVD-video uses a different video codec than WMV files. So, to make a normal DVD-video, you must convert the video.
I suggest using AVStoDVD for this conversion. It is free to use: http://www.videohelp.com/software/AVSTODVD When you have finished the conversion, burn to a disc with ImgBurn, or your regular burning program.
I have written a guide for using AVStoDVD. You can find the link just below, in my signature.