Depends on your phone - check the setting when you're in the camera and in video mode.
If you don't have the option to change the phone, you could get a video converter for you PC and run the video from the phone through it.
A way easier option, though would be to simply get a video player that supports MP4 for your PC. There are heaps of these available and many are free. Just Google "MP4 video player windows". Be sure to get your download from a reputable source.