You'll need to add the following lines to /etc/rc.d/rc.local:

	# Start vboxdrv
	if [ -x /etc/rc.d/rc.vboxdrv ]; then
	  /etc/rc.d/rc.vboxdrv start
	fi

This will load the support kernel module for VirtualBox. 


You'll then need to add the following lines to /etc/rc.d/rc.local_shutdown:

	# Stop vboxdrv
	if [ -x /etc/rc.d/rc.vboxdrv ]; then
	  /etc/rc.d/rc.vboxdrv stop
	fi


Any user accounts that plan to use virtualbox will need to be members
of the "vboxusers" group.