Can't resize Windows HVM permanently

[Misterblue]

Recently I switched to xfce instead of KDE and I noticed while before could change the size of screen very fast and after shutdown returned to the same size, in xfce I have to move the window with the mouse till it doesn't return more to default automatically and after is possible to resize (right button of mouse on the title bar). Furthermore I have also to do it every time that I restart it.

Some help?

Thank you