Preston began the brightest as John Welsh and new signing Stuart Beavon both went close.
Crawley's first notable effort came when winger, Nicky Adams saw his 25-yard strike go just wide of 'keeper Thorston Stuckmann's top right-hand corner.
Soon after, on 26 minutes, Mat Sadler's left wing cross was headed just wide by Dannie Bulman. An opportunity for a rare goal from the fans' favourite.
Akpo Sodje was booked for Preston just prior to fracas between both sets of players as Kyle McFadzean was chopped down from behind by Lilywhites skipper Nicky Wroe. Somehow the referee felt a few words would suffice rather than a straight red card.
|Wroe's challenge deserved more than just a chat|
Within 3 minutes of the second half resuming, the visitors had another effort as McFadzean let fly from long range. The defender's header, however, was straight at Stuckmann.
The breakthrough finally came on 54 minutes as Adams' superb deep cross from the left hand side saw Alexander, who rose above Scott Laird to send the away stand into raptures.
Alexander added to his tally four minutes later when he turned North End centre back, Shane Cansdell-Sheriff and fired into the bottom right -hand corner with the outside of his right boot.
The Reds captain had a chance to complete his hat-trick but headed tamely at Stuckmann from another Sadler cross.
Westley decided to take off danger man Jeffrey Mounakana. The former Arsenal man making way for William Hayhurst with 12 minutes of normal time remaining.
Preston snatched a goal back at the death as an in-swinging Byrom free kick found Paul Huntington lurking in the box and the big defender fired past away 'keeper Paul Jones, just before the referee added 5 extra minutes of injury time.
One final chance fell to the home side as the natives found their voice; Wroe tried to head an effort past Jones, only for the former Peterborough stopper to tip over the bar.
Two successive corners ensued but North End couldn't find a way through a resolute defence.
REDS: P.Jones, Sadler, Connolly, McFadzean, Alexander (c), Hunt, Ajose (Clarke, 79), Bulman, Adams, Cooper, M.Jones (Walsh, 87)