Hardtechno refers to a style of Techno, which evolved after 2000 from Schranz and Hardcore Techno. While the first harder Techno productions appeared around 1991 on labels such as PCP and Industrial Strength, these were referred to as Hardcore Techno. Over the years, the Hardcore scene cultivated a new sound far away from its Techno origins, whereas Techno itself went in a softer direction.
At the end of the 1990s, fueled by the Schranz movement, a new, extremely hard style of Techno became popular, which is now generally referred to as Hardtechno. This style runs at very high bpm, usually 150 or more and features heavy distortion and prominent kickdrums. By 2007, almost all major European Techno festivals, such as I Love Techno, Awakenings, MayDay, Nature One, Mystery Land featured a Hardtechno stage or at least one Hardtechno artist. It has also been the main focus of festivals like "Hardtechno Festival" in Vienna (attendance 2,000+) or Syndicate in Dortmund (attendance 10,000).
...more info at http://en.wikipedia.org/wiki/Hardtechno