Axence nVision Free is the free version of a very powerful network scanning, monitoring and management tool.
At its simplest, Axence nVision Free can be used as a network discovery tool. It scans your network, discovers any connected systems and devices, lists their TCP/IP services, and helps you create network maps.
The program is also a monitoring system. Do you want to know if a host is down, a service has failed, CPU utilisation is high, maybe a new system has connected to the network? NVision can be set up to display a desktop alert or send an email.
Simple inventory tools mean you're able to view some system information details on your connected PCs (some installed software, user accounts, shared folders, startup commands and more). It's relatively basic - the best of this section is reserved for the commercial build - but there's enough here to be useful.
You also get nVision's excellent netTools package, a handy collection of network troubleshooting utilities. There's a visual Ping and Traceroute, bandwidth assessment, host and network scanning, a graphical netstat, even a tool for establishing low-level TCP and UDP connections and monitoring the results.