A first-half brace from Shefki Kuqi followed by a second-half header by Leon Cort gave Palace their most convincing home win of the season.
Peter Taylor's Eagles had given up all hope of a pushing for a play-off place and ironically reserved their best performance of the season despite having nothing to play for but their pride.
Kuqi gave Preston the runaround all afternoon and was boosted by two well-taken goals.
The first on 16 minutes came from a well-placed header into the far corner following Ben Watson's out-swinging corner to the right.
Four minutes later Kuqi was in the action again. Cort's long pass dropped nicely to Clinton Morrison in the right channel and his immediate cross was met perfectly by Kuqi, who finished off with a right-foot volley which flew into the top corner.
Preston's only worthwhile effort arrived on 20 minutes when Brett Ormerod's shot from 15 yards out was driven straight at Gabor Kiraly.
Ormerod had a chance early in the second half but fell over in front of goal before Cort's 68th minute header wrapped up his afternoon's work for Palace.
Another Watson corner was met perfectly by the tall defender who climbed above the Preston defence with a thumping header into the top corner.
The defeat would have been heavier but for several crucial stops from Andy Lonergan.
Kuqi stretched the young keeper to make two diving stops while Morrison also tested Lonergan.
Watson should have scored after being set up by Morrison and Kuqi went close to completing his hat-trick but shot wide after going clear following a solo run.
It all added up to a convincing win for Palace and for Preston their fifth away successive defeat.