Wikipedia
DxDiag
DxDiag (" DirectX Diagnostic Tool ") is a diagnostics tool used to test DirectX functionality and troubleshoot video- or sound-related hardware problems. DirectX Diagnostic can save text files with the scan results. These files are often posted in tech forums or attached to support emails in order to give support personnel a better idea of the PC the requester is using in case the error is due to a hardware failure or incompatibility.
DxDiag is located in [[%SystemRoot%]]\System32. Starting from Windows Vista, DxDiag only shows information; it is no longer possible to test the hardware and the various DirectX components.