Try writing the output file as a .CSV file or .DBF file instead of .XLS. It looks the same when you open the output file in Excel, but bypasses the 16,384 row maximum for early versions of Excel. This is a limitation of versions of Monarch before 6.1, not the version of Excel installed on your machine.
Some Excel trivia: Versions of Excel before 7.0 had 16,384 rows because that's 2 to the fourteenth power. Current versions of Excel have 65,536 rows which is 2 to the sixteenth power.