Nedd to put another text-addition to state it more precise:
There is actually no need to to install guest-additions from within Ubuntu via KpackageKit (Synaptic Package Managment), if it is run as guest.. The Guest system gets established from the Host-System (this is in your case Windows) supplied with the package you downloaded from VirtualBox.org
The guest-addition must be installed via vboxmanage as it lies within the host-system
Nedd to put another text-addition to state it more precise:
There is actually no need to to install guest-additions from within Ubuntu via KpackageKit (Synaptic Package Managment), if it is run as guest.. The Guest system gets established from the Host-System (this is in your case Windows) supplied with the package you downloaded from VirtualBox.org
The guest-addition must be installed via vboxmanage as it lies within the host-system