Regina M.Lahti;68;of Arnold City;died Sunday;Nov.17;1996;at home.  Born Oct.10;1928;in Monessen;she was the daughter of the late Louis and Stella Dembeck Czajkowski.  She was Catholic by faith.  In addition to her parents;she was preceded in death by her husband;David Lahti;on Dec.22;1993;and three brothers.  Surviving are one daughter and son-in-law;Diane L.and John Boozer of Belle Vernon;one brother and sister-in-law;Joe and Genevieve Cekoski of Belle Vernon;one grandson and his wife;William D.and April Sethman;one great-grandson;Cody David Sethman;and three step-grandchildren.  Friends will be received Tuesday from noon to 7 and 7 to 9 p.m.and Wednesday until 10 a.m.in the Howard W.McCrory Funeral Home;Fayette City.  Burial will be in Belle Vernon Cemetery.