Communications access is one area that shares DLLs. The program merely calls the appropriate DLL to retrieve the drives that are available on the computer or across the network. When removing an application, we have not had problems with deleting DLLs when prompted. Still, better safe than sorry. If the message indicates that other programs share the DLL, leave it on the machine and do not delete.
Performance is the major reason for going to a switched network design.
The hub acts as a sharing concentration point. When a switch is installed, your computer only sees the traffic destined for itself and any broadcast traffic that needs to get to all machines. Your computer doesn't care if Mary's computer is opening a file on the server or if Phil is researching a case via the Internet. A switch would isolate that network traffic and keep it away from your computer, thereby increasing the amount of available bandwidth to you. This is a very simple explanation and network designs have several other considerations for efficient traffic movement.