Fastpush is a Windows-specific script that can be used to remotely 
install WinVNC onto a large number of computers. These target
computers must be running NT, 2000 or XP, and you need admin rights 
to do this, but if you're looking for the best way to install VNC
into your whole LAN, this is it.

You can get a free copy here: http://www.darkage.co.uk/