Fulham midfielder Steed Malbranque gets the first goal at Old Trafford

Ruud van Nistelrooy's second successive FA Cup double saw Manchester United advance to the semi-finals for the first time since 1999.

The flying Dutchman, whose goals sent Manchester City spinning out of the competition in the previous round, smashed home close-range efforts either side of the interval to dismantle a battling Fulham side who had gone in front midway through the opening period through Steed Malbranque's firm spot-kick.

Although they were never at their most fluent, United just about deserved a success that keeps their hopes of domestic silverware alive and leaves them in good heart ahead of Tuesday's equally crucial Champions League encounter with Porto.

Recent history suggests United are never more dangerous than when their backs are firmly against the wall.

With just one win in five games, nine points adrift of champions-elect Arsenal and lacking an entire first-choice defence, this was definitely one of those occasions, so it was no surprise they started with drive and purpose.

Ryan Giggs had a chance to put the hosts ahead inside the first minute but saw Alain Goma block his close-range effort from Cristiano Ronaldo's cross.

It proved to be an unhappy foretaste of the Welshman's day for either side of the interval he wasted similar opportunities, smashing a side-footed shot into a crowd of Fulham defenders after Ronaldo had again caused panic in the visitors' box, then allowing Edwin van der Sar to make the save after Darren Fletcher had provided the killer pass.

Van Nistelrooy also wasted an excellent chance to break the deadlock when Fulham failed to clear yet another low Ronaldo cross, blazing over from eight yards.

Fortunately, the prolific Dutchman was not as was wasteful with his next effort, which he crashed home on the half-volley after Giggs had added the perfect low cross to the pass from Paul Scholes that sent him scampering down the left flank.

It was van Nistelrooy's 25th strike of another successful personal campaign and it came as blessed relief to the home side, who had fallen behind two minutes earlier.

Wise counsel suggests the midweek arrival of Walter Smith as Ferguson's assistant was a move designed specifically to shore up a backline that had leaked goals in the absence of Rio Ferdinand.

Stood in the dug-out alongside his long-time friend, Smith must have been ripping his hair out at the combination of ill-advised moves that culminated in the first penalty United have conceded on home soil in domestic combat for 11 years.

If skipper and stand-in centre-half Roy Keane had opted to clear his lines rather than try to let an aimless pass run out for a goal-kick, the move would never have started. Instead, it gave Brian McBride the opportunity to slide in, rob the Irishman and push a pass into the box aimed at Luis Boa Morte.

Wes Brown looked favourite to get there first but inexplicably, the England international missed the ball completely and succeeded only in wiping out Boa Morte, leaving referee Rob Styles with no option but to award the spot-kick which Malbranque smashed home with clinical efficiency.

Had van Nistelrooy not levelled almost immediately, a United side lacking in confidence might have struggled to recover. Instead, they took heart from the goal and inspired by the industry of Nicky Butt and Fletcher, plus the trickery of Ronaldo, they gradually assumed control.

Ronaldo has been something of an enigma since lighting up Old Trafford on his debut against Bolton back in August but the glimpses of class he has shown since then all came together this afternoon in one mesmerising display that ran Fulham ragged.

In addition to his outlandish dribbling skills, Ronaldo also curled a free-kick onto the crossbar and then set up van Nistelrooy for his second, latching onto another astute Fletcher pass before providing the Dutchman with a tap-in.

Fulham desperately pushed forward looking for an equaliser that never really looked like coming, even though the departure of Keane 15 minutes from time saw United finish the game with Ryan Giggs occupying an unaccustomed left-back berth.

Man Utd Howard, Phil Neville, Brown, Keane (Djemba-Djemba 75), O'Shea, Fletcher, Butt, Scholes, Ronaldo (Solskjaer 88), van Nistelrooy, Giggs.

Subs Not Used: Kleberson, Forlan, Carroll.

Booked: Keane, Phil Neville.

Goals: van Nistelrooy 25, 62.

Fulham Van der Sar, Volz, Knight, Goma, Green, Malbranque, Sean Davis, Legwinski (Pembridge 64), Clark (Petta 81), Boa Morte, McBride (Hayles 63).

Subs Not Used: Crossley, Djetou.

Booked: Volz(55,f), Boa Morte(58,f), Goma(90,f), Hayles(90,f).

Goals: Malbranque 23 pen.

Att: 67,614

Ref: R Styles (Hampshire).