EnumWindows returns windowhandles, FindWindow uses the windowtitle as second argument, and returns the window handle of the first window found. If you load your list by enumwindows, your list contains windowhandles, and not window titles. You don't need to use FindWindow anymore, since you already have the window handle. You could use GetWindowText to get the title (if that is what you want).
BTW if you don't want to pass the first argument, you can use vbNullString, I'm not sure if passing 0 will have the same effect.