I'm having difficulty working out the windows 7 family pack. It seems to be labelled as an upgrade, does that mean that it's on;y worth purchaing if you have 3 PCs with windows already installed? I can't do clean installs on 3 sepererate PCs? Thanks.
All upgrade media can do clean install, just you'll have to provide a proof when it requested for it. This has been the case for the last 20 years with any Windows upgrade, either a binary check on the existing Windows installation, or Windows installation media.