Sophos AntiVirus allows you to either install it on each workstation or deliver it from the server. You can designate a PC as your server, but it will only be able to administer 10 PCs in a workgroup and therefore each time you require multiple installations a new 'server' must be assigned for the new workgroup. This means it is ideal for the smaller business model, but although scaleable may not prove ideal for the larger SME.