DRG A RTRN FLT AT NGT TO DECATUR, AL, THE PLT NOTED HIS WX RADAR WAS INOP. HE VISUALLY AVOIDED THUNDERSTORMS (TSTMS), WHICH HAD BEEN FORECASTED. WHILE AVOIDING TSTMS, HE NOTED A REDUCTION IN ENG POWER, A SLIGHT YAW, INDCNS OF FUEL FLOW IRREGULARITY & THAT THE LEFT & RGT BOOST PUMPS WERE INOP. THESE OCCURRED AT ABOUT THE TIME, HE SAW A WHITE ARC WHICH HE SAID HAD JUMPED FROM THE PROP, SPINNER OR NACELLE AREA TO THE ACFT'S NOSE. DUE TO THE WX, HE ELECTED TO DIVERT TO PADUCAH. AFTER THE ARPT WAS IN SIGHT, HE NEEDED TO LOSE ALT BEFORE LANDING & WAS CLEARED TO MAKE A 360 DEG TURN. WHILE TURNING, HE LOST SIGHT OF THE ARPT, THEN ROLLED OUT ON THE WRONG HEADING & STARTED FLYING TOWARD A STROBE LIGHT AT AN INDUSTRIAL COMPLEX. WHEN HE REALIZED HIS ERROR & SAW THE ARPT, HE TURNED TOWARD THE RWY; BUT AS HE WAS MANEUVERING, THE ACFT LOST ALT, HIT TREES & CRASHED. AN EXAM OF THE ENGS & FUEL PUMPS REVEALED NO INDCN OF A PREIMPACT FAILURE. NO PHYSICAL EVIDENCE OF A LIGHTNING STRIKE WAS FOUND, BUT THE NOSE & ENGS WERE BADLY DAMAGED FROM IMPACT.