A Hardware Key is included with the HCM/Cinema and SIG/Cinema software to prevent unlicensed use.  The Hardware Key attaches to the parallel port of your computer. 

If you purchase the standard non-Network Version of the software, you receive a Key for each PC covered in your license.  For example, if your license covers 2 PCs, you can simultaneously use the software on the two specific PCs which have non-network keys attached. 

If you purchase a Network Version of the software, (at an additional cost of $395 US), you receive a single "Network Key" which must be attached to the parallel port of any computer on the network.  Special driver software is installed on the computer attached to the Network Key, and this computer must be on whenever anyone on the network uses HCM/Cinema or SIG/Cinema.  The Network Key is programmed to allow simultaneous access to the software by as many individual PCs on the network as are included in your license.  For example, if your license covers 2 PCs, the Network Version will allow you to simultaneously use the software on any 2 PCs on the network. 

You can always upgrade your license to cover additional PCs as necessary with either the non-Network or Network Version.