Four weeks after being outclassed by Manchester United, West Ham returned to Old Trafford to end their hopes of winning the Treble again.

West Ham had been totally outplayed by United on New Year's Day as the Reds produced the kind of performance which suggested the Treble was within their capabilities.

But the Hammers, who had lost all 11 of their last visits to Old Trafford, bounced back from that defeat to win this thrilling FA Cup fourth-round tie.

Paolo di Canio, who always seems to save his best for the big occasions, slotted home the decisive goal in the 75th minute to send United crashing to their first cup defeat in nearly three years.

Incredibly it was the first time Sir Alex Ferguson had lost at home to West Ham in his 14-year reign as manager and the first time United had lost in the FA Cup at Old Trafford since they lost on penalties to Southampton nine years ago.

West Ham began positively and manager Harry Redknapp fielded Frederic Kanoute as a lone striker with the fired-up di Canio supporting him at every opportunity.

Redknapp also selected an exciting midfield of Joe Cole, Michael Carrick and Frank Lampard and from an early thrust new boy Sebastien Schemmel blazed wide.

Carrick then beat two United players before shooting just wide of Barthez's goal.

The tie was coming nicely to the boil and Shaka Hislop, who is carrying a knee injury, nearly gifted United a goal when he sliced Christian Dailly's backpass only for Hannu Tihinen to hoof the spinning ball clear of the West Ham goal.

Ryan Giggs began to cut loose down the left. He crossed to Andy Cole, who got the nod ahead of Ole Gunnar Solskjaer, and after his first attempt was blocked he headed over when the ball rebounded to him.

Giggs then played a one-two with Teddy Sheringham before hitting a drive, which Hislop touched behind for a corner.

The Welshman should have done better following a flowing United move in the 34th minute.

Sheringham played a pass through to Cole, who laid it off to David Beckham on the right and he sent over a teasing cross to Giggs at the back post, but the winger knocked the ball the wrong side of the post.

It was all United now and Nigel Winterburn chopped down Gary Neville in prime Beckham territory just outside the box on the right-hand side.

Up stepped the England captain and he whipped a right-foot shot over the West Ham wall only for Hislop to touch his effort over the bar.

Tihinen produced a goalline clearance to deny Sheringham what would have been his 19th goal of the season after the United striker had been played in on the right by Denis Irwin.

Carrick was having a fine game in front of the watching Sven-Goran Eriksson and the youngster hit a left-foot shot from just inside the box, which was saved by Barthez.

The Reds squandered a great chance to score when Hislop parried Cole's shot and Sheringham blazed over from the rebound with the goal at his mercy.

Hislop denied United again a minute later when he held a Giggs shot at the second attempt.

The chances were coming at both ends and Cole stung Barthez's with a right-foot drive and the Frenchman managed to touch the ball away from Kanoute as he followed up.

The tempo dropped, but as it did West Ham's hopes of earning a replay grew.

Those hopes were endangered when Dailly gave away a free-kick on the edge of the area for handball only for Beckham to shoot against the wall.

Then came the only goal which the home side felt should have been disallowed for offside.

Kanoute played di Canio through and the Italian slotted the ball home past Barthez for his 11th goal of the season.

United's responded by throwing Solskjaer and Dwight Yorke on to leave West Ham with four strikers to contend with.

The closing minutes were a real kitchen sink job and West Ham survived a penalty appeal for handball against Winterburn.

Barthez joined the attack, but for once United's famed powers of recovery failed them and West Ham were left to celebrate the finest win for many a month.

Teams:

Man Utd: Barthez, Irwin (Solskjaer 78), Silvestre, Stam, Gary Neville, Beckham, Giggs, Keane, Butt (Yorke 79),Sheringham, Cole.

Subs Not Used: Van Der Gouw, Phil Neville, Chadwick.

Booked: Beckham.

West Ham: Hislop, Tihinen, Stuart Pearce, Dailly, Schemmel, Winterburn, Lampard, Cole (Ian Pearce 90), Carrick, Kanoute, Di Canio (Soma 89).

Subs Not Used: Forrest, Potts, Moncur.

Goals: Di Canio 76.

Att: 67,029

Ref: P Durkin (Dorset).