THE PLT SAID ALL PRE-FLT PREP WERE NORMAL INCLUDING AN ENG RUN-UP. THE TAKEOFF WAS BEING MADE WITH LIGHT WINDS. AFTER ROLLING ABOUT 300 FT THE ACFT BEGAN A SWERVE TO THE RT WHICH THE PLT PERCEIVED WAS ASSOCIATED WITH A LOSS OF PWR ON THE RT ENG. THE PLT INITIATED AN ABORT AND BEGAN HEAVY BRAKING. THE ACFT CONTINUED IN A RT SWERVE AND DEPARTED THE RT SIDE OF THE RWY. THE FIELD ADJACENT TO THE RWY WAS PLOWED AND WAS ROUGH AND UNEVEN. WHEN THE NOSE WHEEL ENCOUNTERED A 12 IN DEEP FURROW THE NOSE GEAR COLLAPSED AND THE ACFT NOSED OVER. FAA EXAMINED THE WRECKAGE AND COULD NOT FIND ANY EVIDENCE TO EXPLAIN THE REPORTED LOSS OF PWR. THE INSPECTOR SAID LOCKED BRAKE SKID MARKS WERE FOUND ON THE RWY WHICH COULD BE ASSOCIATED WITH THE MAIN GEAR OF THE ACDT ACFT. HE SAID THE SKID MARKS BEGAN OPPOSITE EACH OTHER AND LED TO THE FINAL RESTING PLACE OF THE ACFT.