start dxdiag.exe on you computer will give you information about system, display sound and inputs, also you can use cpuz, to find out more detailed things about you cpu. Also you can go to manage devices to see what you have connected and what versions are they.
But if you do not need this diagnostics, but just information about your computer, because info and diagrnostics are different things, then use dxdiag.exe, just type it into start and run (xp) or start and type dxdiag (vista) it will give you information