First...
I've found the use of docking feature
Second...
I (maybe) found a bug.
If I dock the contact list window to the left, I can't move it again, eventhough I've unchecked the box.
I also can't maximize the window.
err..
Sometimes, I admit, I can do it.
To "fix" it, it should be closed and opened it from the systray.
Thank you.