Total Network Inventory: Professional PC audit and network inventory management software - fits best for a for companies of all sizes. Free for 60 days.
Speccy - Speccy - find the details of your computer's specs. Great for spotting issues or finding compatible upgrades. Download the latest version free.
Network Inventory Advisor - Network Inventory Advisor audits all network software and hardware simply and efficiently
CPU-Z - CPU-Z is a freeware that gathers information on some of the main devices of your system : Processor name and number, codename, process, package, cache levels.
Lansweeper - Lansweeper discovers Windows, Linux and Mac machines in your network.
AIDA64 - AIDA64 is a system information, diagnostics and benchmarking solution for Windows PC.
Nmap - Nmap Free Security Scanner, Port Scanner, & Network Exploration Tool. Download open source software for Linux, Windows, UNIX, FreeBSD, etc.