THE PLT HAD PURCHASED THE ACFT AT REXBURG, ID ON THE DAY OF THE ACCIDENT. REPORTEDLY, THE PREVIOUS OWNER HAD FLOWN WITH THE PLT, BEFORE THE PLT DEPARTED REXBURG, AND SAID HE HAD FLOWN THE ACFT VERY WELL. THE PREVIOUS OWNER STATED THAT THE DME WAS NOT FUNCTIONING AT THE TIME THE ACFT WAS PURCHASED & HAD LEFT REXBURG. THE PLT THEN DEPARTED ON A FLT TO POTEAU, OK WITH AN EN ROUTE STOP AT HUTCHINSON, KS. AT HUTCHINSON, THE ACFT WAS REFUELED, BUT NO MAINTEANCE WAS PERFORMED. THE PLT TOOK OFF ON THE FINAL PORTION OF THE FLT TO POTEAU AT 1905 CST. DURING ARRIVAL, HE WAS INSTRUCTEDTO REMAIN AT 4500 FT UNTIL CROSSING THE RICH MOUNTAIN VOR, THEN WAS CLEARED FOR THE VOR/DME RWY 36 APCH. DURING THE, APCH, THE ACFT COLLIDED WITH RISING TERRAIN AT ABOUT 2550 FT, APRX 2 MI NORTH OF THE VOR. THE MIN STEP-DOWN ALT WAS 4000 FT UNTIL 8 MI NORTH OF THE VOR, THEN THE MIN ALT WAS 2400 FT UNTIL CROSSING THE FINAL APCH FIX, 15 MI NORTH OF THE VOR. NO PREIMPACT MALFUNCTION WAS FOUND EXCEPT FOR THE INOPERATIVE DME.