aus301 said...it's much the same as rollerblade vs in line skate.
windsurfer is a brand, sailboard is the name of the sport, however most just call it windsurfing after the most well known brand of the early days (same as rollerbladeing)
Geez I even remember people saying they are going to hoover the carpet

From the US Patent and Trademark Office database-
Mark WINDSURFER
Goods and Services (EXPIRED) : SURFBOARDS. FIRST USE: 19690815. FIRST USE IN COMMERCE: 19690815
Serial Number 72433306
Filing Date August 21, 1972
Registration Number 0962616
Registration Date July 3, 1973
Owner (REGISTRANT) WINDSURFING INTERNATIONAL, INC. CORPORATION CALIFORNIA 1808 STANFORD AVE. SANTA MONICA, CALIF.
Live/Dead Indicator DEAD
Mark WINDSURFER and logo
Goods and Services (CANCELLED) : Sailboats Having a Free Sail System. FIRST USE: 19690815. FIRST USE IN COMMERCE: 19690815
Serial Number 73145428
Filing Date October 20, 1977
Registration Number 1195641
Registration Date May 18, 1982
Owner (REGISTRANT) WINDSURFING INTERNATIONAL, INC. CORPORATION CALIFORNIA 1955 WEST 190TH STREET TORRANCE CALIFORNIA 90291
Attorney of Record NILSSON, ROBBINS, DALGARN, BERLINER ETAL
Prior Registrations 0909519;0962616;0997974
Live/Dead Indicator DEAD
Cancellation Date February 22, 2003
Word Mark WINDSURFER
Goods and Services SAILBOATS COMPRISING A SURFBOARDTYPE HULL AND A SAIL. FIRST USE: 19690815. FIRST USE IN COMMERCE: 19690815
Serial Number 73008013
Filing Date December 3, 1973
Registration Number 0997974
Registration Date November 12, 1974
Owner (REGISTRANT) WINDSURFING INTERNATIONAL, INC. CORPORATION CALIFORNIA 621 STONE CANYON ROAD LOS ANGELES CALIFORNIA 90077
Attorney of Record BILLY A. Prior Registrations 0909519;0962616
Type of Mark TRADEMARK
Renewal 1ST RENEWAL 19950731
Live/Dead Indicator DEAD
WINDSURFER was the trademark coined and registered by Windsurfing International. At the time undar US law, their registrations wouldn't have stopped people from using the mark as a generic description to describe the sport, but they could have stopped other traders from using the word WINDSURFER in relation to their products. (For those who are interested (probably no-one) there has since been a change in US law so trademark owners can prevent "dilution" of their registered marks by generic misuse by others. There are no similar anti-dilution laws in Australia.)
However, over many years of misuse by the public and inadequate remedial action by Windsurfing International, the mark has fallen into generic use. The trademark registrations have also died.
None of this answers what the "correct" name for the sport is, just as long as it ain't called "kiting"

And it's interesting to see how Windsurfing International described their goods as "surfboards" and "sailboats having a free sail system".