Manchester United were favored to draw away from home by most experts, but were looking at their fourth loss in six matches when the second-half whistle blew.
Despite dominating possession (match ended with United at 67 percent to the Hammers at 33 percent), United's defense looked sluggish, especially Nemanja Vidic, who is clearly not 100 percent after recovering from a calf injury over the international break.
The Patrice Evra handball was bad luck on the Frenchman's part after being left alone against Carlton Cole following a long ball out of the Hammers' defense. He conceded the first penalty for the Red Devils, which Mark Noble had no problem converting.
Only a few minutes later, Vidic was caught out of position on the edge of the box against Cole, resulting in a bad tackle leading to the Hammers' second. Some may argue that first contact was on the edge of the box, but Lee Mason pointed to the United penalty spot where Mark Noble calmly drove home his second.
However, Sir Alex Ferguson's side came alive in the second half following the introduction of Javier "Chicharito" Hernandez and Dimitar Berbatov.
Rooney slotted home a fantastic free kick shortly after Berbatov's introduction before slicing home a second with his right after beating the West Ham defense inside their own box.
Fabio then made a dangerous run into the box and was lucky to play the ball of Matthew Upson's arm near the Hammer's goal line, which resulted in Rooney's third, taken from the penalty spot.
A few minutes later, Berbatov split the Hammers' defense to set up United's "Mex-Factor," Chicharito, for a simple chip shot into West Ham's net to capture all three points for the Red Devils.
The win gives United some much-needed breathing room at the top of the table with Arsenal set to play Blackburn later this afternoon afternoon.
The long-awaited return of Park Ji-Sung, with Antonio Valencia looking close to top form, means United are starting look much more healthy in the attack from here on out. United were also able to save Nani for the Champions League meeting at Stamford Bridge next week, with the Portuguese attacker only making a late cameo near the match's end.