Laird (28) used to be a downhill specialist and was the top-ranked New Zealand woman internationally last year, at 26th.
She was runner-up in the downhill event at last year's national championships and spent four years competing overseas from 2006-09.
Laird started mountain biking when she was a student at the University of Otago in 2003 but decided last October that she needed a change.
"I'd broken numerous bones and tearing downhill was no longer the same thrill for me," she said.
Laird was naturally nervous about shifting from short downhill races lasting from two to four minutes to the long version of the sport in which races can last up to two hours.
"I needed the change," she said.
"I have found it exciting. My aim this year was just to learn. I had no idea how I would go."
Laird surprised herself by winning the first event of this year's Raboplus-sponsored mountain bike series, in Christchurch, then repeated the performance in Dunedin on Saturday.
Laird won Saturday's race on the Forrester Park-Bethunes Gully course after an exciting duel with Sara MacDonald (Dunedin) by 48 seconds in a time of 1hr 47min 22sec.
MacDonald clocked 1hr 48min 10sec, and Samara Sheppard (Wellington) was third in 1hr 49min 38sec.
"I'd finished second and third but had never won an elite downhill race," Laird said.
"It's been like a dream come true for me."
Laird led strongly and held a four-second lead from Sheppard after the first of the four laps.
MacDonald was three seconds back in third.
MacDonald started in sport five years ago after reaching national prominence in rowing and adventure racing.
She demonstrated her strength when she left Sheppard behind and closed the gap to Laird to five seconds during the second lap.
She completed this lap in 26min 23sec and was two seconds faster than Laird.
The gap closed during the penultimate lap, and the pair battled neck and neck down the steep tracks in the Bethunes Gully forest.
But disaster struck MacDonald as she was coming out of the forest when her chain locked up and she had to get off her bike to fix the problem.
"I lost contact then and Amy was gone," MacDonald said.
Laird gained 10 seconds on MacDonald on the third lap and led by 14 seconds with a lap to go.
Sheppard (19) had run out of gas and was 1min 06sec behind.
Laird got a second lease of energy and sped away from MacDonald on the last lap to win by 48 seconds.
Her last-lap time of 26min 17sec was the fastest of the race.
Other Dunedin-based riders to perform well were Erin Greene, sixth in 1hr 52min 28sec, former national champion Anja McDonald, back in the city after two years overseas, eighth in 1hr 55min 09sec, and Hannah Thorne, ninth in 1hr 56min 09sec.
