COUNTIF with two criteria?

Palmetto, I don't quite follow the SUMPRODUCT, shouldn't it be (A1 issue excepted)

=SUMPRODUCT(($A$1:$A$2793=$A$1)*($C$1:$C$2793>50))

or if preferred using double unary

=SUMPRODUCT(--($A$1:$A$2793=$A$1),--($C$1:$C$2793>50))

again though just to reiterate if indeed you are running XL07 and backwards compatibility is not an issue then use COUNTIFS in preference to SUMPRODUCT.