you can't....
CR is fairly limited in that it will only export to the set displayed. If your version of Excel only displays 65000 rows, than that is the limit and to the best of my knowledge there is nothing you can do....besides reducing the number of rows of data.
Perhaps generating multiple reports that produce the data but stay under the 65000 row count and don't duplicate.
Here is another question, why would you need to export so many rows, if Excel can't handle it, they couldn't use it anyway.
How are they going to use the data, would summary data be good enough, what do they need to know? can it be subdivided so that the both the report and the export work?
HTH