To burn a video DVD, the international DVD standard requires that your wmv files be converted to DVD-compatible mpeg-2. And that format is far less compressed than .wmv, which basically means that the mpeg-2 file will be much larger than the original wmv.
What skier-hughes meant was: what are the properties you selected for the conversion to DVD-compatible mpeg-2. If you just used the default settings, which include a bitrate of 8000 kbps, this will produce a file about the size of the one you actually got. And of course that will not fit on a single layer DVD. You would have to use a dual layer DVD.
To get your 1 hr 45 minute project to fit on a single layer DVD, you would have to reduce the default bitrate to around 4500 kbps, or perhaps 5000 kbps if you used Dolby as the audio format.