Manchester United turned on the style to charge into the FA Cup fifth round and rub salt into West Ham's gaping Premiership wounds.

If West Ham were in need of a boost to take their minds off their awful league form, then Old Trafford was not the place to find it.

Manchester United, already through to one cup final this week, were hungry for more.

Ryan Giggs and Ruud van Nistelrooy both struck twice in an embarrassingly one-sided game, with defender Phil Neville and substitute Ole Gunnar Solskjaer also joining the goalscoring procession.

United's goal haul

8 mins: Giggs slots home the opener 29 mins: Giggs' shot deflects in off Breen 49 mins: Van Nistelrooy fires home the third 50 mins: Phil Neville joins in the goal scoring 58 mins: Van Nistelrooy strikes again 70 mins: Sub Solskjaer completes the rout

It took the home side only eight minutes to break West Ham's fragile resistance.

Ruud van Nistelrooy easily shrugged off Gary Breen to reach David Beckham's pass and tee up Paul Scholes.

Scholes' shot was scrambled off the line by Ian Pearce but the ball fell kindly to Ryan Giggs, who calmly stroked home between a crowd of players on the line.

On the half-hour, the lead was doubled when Giggs, with only one goal in his previous 25 games for United, bagged his second of the game.

Juan Veron teed the winger up on the edge of the box and Giggs' first-time shot looped off Gary Breen and over the helpless David James.

Though this was an all-Premiership cup tie, the balance of play suggested it was Premiership against lower division.

Giggs slots home the opening goal

Manchester United continued to swarm forward and James had to be at his agile best to keep out a curling right-foot shot from Beckham.

But James needed a post to come to his rescue 10 minutes before half-time when a superb series of passes ended with Van Nistelrooy setting up Scholes for a shot against the woodwork.

That denied Scholes a seventh consecutive scoring appearance and the England midfielder was replaced by Diego Forlan at half-time after complaining of feeling unwell.

But the sickly feeling in West Ham's stomachs turned even more sour in the opening minutes of the second half.

Four minutes after the restart, Van Nistelrooy's twisting and turning on the edge of the box had West Ham defenders bumping into each other.

And the striker took full advantage of the carnage as he majestically clipped a shot past James with the outside of his right boot.

Seconds later, West Ham's balsa wood defence was shattered again as full-back Phil Neville played a one-two with Forlan and skipped clear to clip a left-foot shot over James.

Giggs and Phil Neville got among the goals

The goal doubled Neville's tally for the season and United could easily have doubled the scoreline in an embarrassingly one-sided game.

Van Nistelrooy, revelling in so much space he must have felt lonely, added the fifth with half-an-hour still to play.

Beckham played a pass through the legs of the hapless Pearce and, as the centre of West Ham's defence yawned once more, Van Nistelrooy pounced to lash home his second goal.

The Dutchman then turned provider for United's sixth 20 minutes from time, turning and playing a precise ball for substitute Ole Gunnar Solskjaer to run on and smash home.

West Ham should have had a late penalty when Gary Neville clipped the ankles of Joe Cole, but a late goal would have been little consolation for Glenn Roeder's ailing Hammers.

Man Utd: Barthez, Gary Neville, Ferdinand, O'Shea, Phil Neville, Beckham (Solskjaer 63), Veron (Butt 51), Keane, Giggs, Scholes (Forlan 45), van Nistelrooy.
Subs Not Used: Carroll, Brown.

Booked: Veron.

West Ham: James, Lomas, Breen (Dailly 80), Pearce, Minto, Bowyer, Cisse (Garcia 80), Carrick, Sinclair (Johnson 80), Defoe, Cole.
Subs Not Used: Van Der Gouw, Hutchison.

Booked: Defoe, Minto.

Attendance: 67,181

Referee: S Bennett (Kent).