A star-studded game on Saturday, the proceeds of which will go to the club's foundation, saw Van Nistelrooy, Edwin van der Sar, Dwight Yorke and Louis Saha among the big names to turn out for United.
The Barca side contained Edgar Davids, Eric Abidal, Edmilson, Gaizka Mendieta and Patrick Kluivert.
Van Nistelrooy delighted home fans with a trademark penalty, before Danny Webber also netted for United in the first half, with second-half Barca goals from Luis Garcia and Mendieta giving the Catalans a draw on the day.
Former United manager Alex Ferguson was among those in the stands as the two sides held a minute's silence ahead of kick-off to pay their respects to the victims of recent terror attacks in Manchester and Barcelona.
United, who were managed on the day by Andy Cole as a replacement for Bryan Robson, won 3-1 in the Camp Nou leg of the tie in June.