Hmm... the problem is that SDL creates the window automatically for you, so if I call this function I'll end up creating another window.
Is there a way to modify the x and y values after the window was created?
EDIT: Never mind, I *finally* found it at google.
SDL_SysWMinfo i;
SDL_VERSION( &i.version );
if ( SDL_GetWMInfo ( &i) ) {
HWND hwnd = i.window;
SetWindowPos( hwnd, HWND_TOP, x, y, width, height, flags );
}