United took the honours in terms of possession and chances created and it took a couple of fine saves from Paul Robinson to keep us in the game in the second half.
Van Nistelrooy's moment came after 41 minutes. Ronaldo crossed deep and John O'Shea fell under Erik Edman's challenge. The Swede certainly had hold of O'Shea's shirt and Van Nistelrooy made no mistake from the spot.
Despite starting with Jermain Defoe, Fredi Kanoute and Robbie Keane, chances were at a minimum and we were kept at distance.
The closest we came to an equaliser saw Roy Carroll save well from both Simon Davies, a volley from 20 yards and, with a minute left, a decent scrambling save to his right to deny Keane. Defoe and Kanoute barely had a sniff all afternoon.
Before that, Pedro Mendes almost capitalised on a poor clearance from Silvestre that left Carroll out of position but the United keeper was back in time to tip the dipping volley wide.
At the other end, Robinson had to keep his eye on a twice-deflected effort from Van Nistelrooy in the first half and following Van Nistelrooy's disallowed goal, did well to block as Ronaldo cut in from the right.
Keane dived in to block a certain goal as Ronaldo's corner fell to Silvestre and then the save of the game as Robinson somehow kept out David Bellion's point-blank header.
MINUTE BY MINUTE GUIDE
3mins: Mabizela clumsy challenge in box, luckily Heinze didn't go over and nothing given.
7mins: Naybet near-post header from Keane's free-kick, difficult angle, sailed over.
9mins: Smith stooping header from Ronaldo's free-kick, no power, comfortable for Robinson.
14mins: Robinson out of box to meet Smith, clearance fell to Ronaldo, 40 yards out, attempted shot with Robinson scrambling back but Naybet back to clear.
15mins: Superb block by Edman to deny Giggs.
21mins: Good cover from Heinze to nod away Keane cross heading for Kanoute.
24mins: Mendes intercepted Silvestre pass and blasted over from 25 yards.
26mins: SAVE. Van Nistelrooy drove ball into box, deflected off Mabizela and King but Robinson alive to it and grasped low to his left.
28mins: CLOSE. Giggs away from Mendes and curled just wide from 20 yards.
29mins: SUB. Davies for Kanoute, possible hamstring.
38mins: SAVE. Poor clearance from Silvestre, Carroll out of position, Mendes dipping volley straight back that Carroll did well to claw away.
41mins: PENALTY. Edman dragged back O'Shea as he went for deep Heinze cross, no doubts that it was a penalty. Robinson dived right way but Van Nistelrooy's spot kick too powerful. 0-1.
Half-time: Spurs 0, United 1
47mins: CHANCE. Smith cut across Naybet, attempted to lift ball over Robinson, just wide.
49mins: Defoe skipped away from Ferdinard but sliced wide from 20 yards.
60mins: YELLOW. Mendes for foul on Ronaldo, although replays showed he won ball.
61mins: DISALLOWED. Ronaldo drove across goal, Van Nistelrooy tapped in at far post, flag up.
64mins: SAVE. O'Shea spread play to Ronaldo who cut inside Edman and hit low to near post, Robinson fine block.
66mins: SUB. Jackson for Mabizela.
67mins: PENALTY? Ronaldo actually kicked the floor as Pamarot tracked burst into box.
69mins: Davies left-foot volley from 22 yards straight at Carroll.
72mins: BLOCK. Giggs corner found its way through to Silvestre at far post but Keane denied certain goal.
82mins: SUB. Miller for Giggs.
84mins: Robbie Keane floated volley always going wide.
85mins: Redknapp 30-yarder always going wide.
85mins: SUB. Bellion for Van Nistelrooy.
88mins: SAVE. Robinson point-blank stop from Bellion's header inside six-yard box.
89mins: Keane battled to win possession on edge of box, volleyed loose ball but Carroll up to it.
Injury time: Late scramble but fall wouldn't fall kindly.
Line-ups: Spurs: Robinson, Pamarot, King, Naybet, Edman, Mabizela (Jackson, 66), Redknapp, Mendes, Keane, Kanoute (Davies, 29), Defoe. Subs: Keller, Brown, Gardner.
Manchester United: Carroll, Heinze, Ferdinand, Brown, Silvestre, Ronaldo, Keane, O'Shea, Giggs, Van Nistelrooy (Bellion, 85), Smith. Subs: Ricardo, Neville, Kleberson, Miller.
Referee: Mr P Walton.
Ruud Van Nistelrooy's penalty ended our unbeaten start to the season in a game that never really caught fire at the Lane.