In the driving snow, United avenged their recent early cup exit against the Pars with a deserved victory in this hard fought tussle.
The visitors almost opened the scoring in the third minute. From Barry Nicholson's corner, Andrius Skerla's powerful header from eight yards flew off Alan Archibald on the goal line and rebounded to safety.
As the game staggered along with neither team taking the upper hand, Stevie Crawford took advantage of a Mark Kerr mis-kick in the 12th minute with a low, long-range shot, but Paul Gallacher was well positioned to save.
It took United 15 minutes before they created their first real chance. Andy McLaren controlled Archibald's cross just inside the box before knocking the ball through for Jim McIntyre to rush in and hit the ball off the diving Derek Stillie.
With the keeper struggling for the rebound, Scott Thomson reacted first to boot the ball to safety.
The Pars tried to move up a gear. Nicholson drilled in a fine pass for Crawford who spun round and cracked a stinging shot that the keeper superbly tipped around the post.
The United support, shivering in the chill, were warmed five minutes after the break with an excellent move between McIntyre and Charlie Miller, which ended with the latter blasting narrowly wide.
Then McLaren flicked on Mark Wilson's cross moments later for Barry Robson to volley past the post.
This seemed to lift the Terrors and they gladly opened the scoring in the 57th minute with wonderful goal from McIntyre.
Miller began the move with a piece of magic on the left. The midfielder mesmerised Skerla before cutting the ball into McIntrye. With two defenders covering, the striker turned the ball on to his favoured left foot before whipping a 16-yard drive into the far corner past the arms of the diving Stillie.
Dunfermline pushed four men forward for the final ten minutes. But it was immaterial as for all the effort from the Pars, they could have continued to have played for another 90 minutes in this manner and would still not have scored a goal.