Can't believe they don't include "always on top" as an option.
Found a solution for those who don't want to mess with the registry:
All the usual programs I use to make a window "always on top" (such as FileboxExtender) don't work with WINDVD9. Found a small utility called ALWAYS ON TOP MAKER which solves the problem.
It's really bare bones, doesn't even indicate if it's running or not, simple hot key turns it on/off, but it works with WinDVD.