ACCORDING TO THE PLT, THE GROUND WAS COVERED WITH ABOUT 6 INCHES OF LIGHT SNOW & THE WIND WAS FROM THE SOUTHWEST AT 5 TO 10 KTS. A SNOW PLOW PRECEEDED HIM TO THE RWY & HAD CLEARED A STRIP ABOUT 10 TO 12 FT WIDE ON THE 1ST 1/3 OF THE RWY. WHEN THE PLT WAS READY FOR TAKEOFF, HE DID NOT SEE THE SNOW PLOW. AFTER WAITING FOR A FEW MINUTES, THE PLT THOUGHT THAT THE SNOW PLOW OPERATOR WAS WAITING FOR HIM TO TAKEOFF, SO HE (THE PLT) ELECTED TO PROCEED WITH THE DEPARTURE. THE PLT STATED THAT AT APRX 50 MPH, DURING THE TAKEOFF ROLL, THE ACFT BEGAN DRIFTING LEFT. HE CORRECTED WITH LIGHT RIGHT RUDDER, BUT REPORTED THE ACFT OVERREACTED. LEFT RUDDER WAS THEN APPLIED. SUBSEQUENTLY, THE LEFT MAIN WHEEL ENCOUNTERED SNOW & THE ACFT VEERED OFF THE RWY. THE PLT PULLED THE THROTTLE TO IDLE, BUT BEFORE STOPPING, THE ACFT HIT A ROCK EMBANKMENT, THE PROP WAS DAMAGED, THE GEAR COLLAPSED & THE LEFT WING WAS DAMAGED.