SiSoft Sandra is a great system information and diagnostics program for Windows. It will provide information on hardware, software and any systems devices.

It works along the lines of other Windows utilities, however it tries to go beyond them and show you more of what's really going on. Giving the user the ability to draw comparisons at both a high and low-level. You can get information about the CPU, chipset, video adapter, ports, printers, sound card, memory, network, Windows internals, AGP, ODBC Connections, USB2, 1394/Firewire, etc.