Lansweeper is free software to make a full hardware and software inventory of your windows network.

Run the server application on as many servers as you like.
Use with unlimited clients in your domain.
Intuitive web interface.
Reporting : over 80 hardware, software, network & server reports included.
Export all data to excel from the reports in the web interface.
Software and operating system licensing reports and cost calculation.
Launch custom commands and programs from the web interface to support your clients (remote control, ping, event viewer, remote screenshot, ...)
Optional scheduled scanning.
Active directory integration
Detailed description »

Changes in the last version:
Windows 7 support
Several bug fixes
New premium tools