i had put avi files on a dvd & they are now nfo files. what happened?

[ChristineSullivan]

i had put avi files on a dvd i have since then reformatted my computer & inserted the dvd & now they are nfo file. what do i do to change it back? they are movies and i downloaded the player i used to view them before which was winamp but it will not open obviously because it is not an nfo file. what did i do wrong?