Do you mean they are dvd files? Dvd files are named VTS_01_1.VOB, VTS_01_2.VOB, and so forth.
If you are using the XP operating system, you may have noticed that it doesn’t come with a dvd decoder built in, and therefore will not play dvds natively. You are required to use third party software. You can download a free media player called VLC for this.
Of course I could be way off base on my guess here. If so, we need more information on what you mean by vts.