AT 1604 EST, THE ACFT DEPARTED FORT WAYNE ON A FERRY FLT. IFR CONDITIONS PREVAILED & THE PLT HAD FILED AN IFR FLT PLAN. WHILE CLIMBING AFTER TAKEOFF, THE PLT PASSED HIS ASSIGNED ALT OF 2500 FT MSL & FLEW TO 4200 FT. ALSO, HE FAILED TO TURN TO HIS INITIAL ASSIGNED HEADING OF 130 DEG. HE HAD PROBLEMS CONTACTING DEPARTURE CONTROL AS HE WAS NOT ON THE ASSIGNED FREQ. HE REPORTED PROBLEMS WITH HIS HEADING INDICATOR & HIS 'GYRO'. SHORTLY AFTER HIS LAST TRANSMISSION, THE ACFT LEFT 4200 FT MSL & CRASHED IN A STEEP DIVE. BEFORE TAKEOFF, THE ATP PLT REPORTED HE HAD FLOWN ALL KING AIR ACFT & WAS CURRENTLY FLYING THE BEECH 200. A REVIEW OF HIS LAST LOG BOOK REVEALED OVER 2000 HRS IN THE BEECH 200, BUT SHOWED NO TIME IN THE BEECH C90. A WITNESS THAT REVIEWED THE ACFT WITH THE PLT BEFORE THE FLT BELIEVED HE (THE PLT) WAS VERY FAMILIAR WITH THE ACFT SYSTEMS. DURING AN INSPECTION OF THE WRECKAGE, NO EVIDENCE WAS FOUND TO VERIFY A PREIMPACT MALFUNCTION OR FAILURE OF THE ACFT OR ENG. ALL INSTRUMENTS WERE DESTROYED.