The pilot reported that during landing, the main landing gear touched down first, followed by the nose landing gear. As soon as the nosegear touched down, the airplane "fishtailed." The pilot applied brakes; however, he was unable to get the airplane to straighten or stop. He then pulled back on the yoke and the airplane veered left. The airplane subsequently traveled off the left side of the runway and struck a ditch. Examination of the airplane by a Federal Aviation Administration inspector revealed substantial damage to the firewall. The inspector did not observe any preimpact mechanical malfunctions, nor did the pilot report any. The recorded wind at the airport, about the time of the accident, was a 30-degree left quartering headwind at 6 knots.