Total Network Inventory: Professional PC audit and network inventory management software - fits best for a for companies of all sizes. Free for 60 days.
Network Inventory Advisor - Network Inventory Advisor audits all network software and hardware simply and efficiently
AIDA64 - AIDA64 is a system information, diagnostics and benchmarking solution for Windows PC.
Lansweeper - Lansweeper discovers Windows, Linux and Mac machines in your network.
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.
Nmap - Nmap Free Security Scanner, Port Scanner, & Network Exploration Tool. Download open source software for Linux, Windows, UNIX, FreeBSD, etc.
Prime95 - Prime95 is a program that searches for new Mersenne prime numbers.