The StatCalc utility in Epi Info™ 3.5.1 is a 16-bit MS-DOS application. The 64-bit versions of Microsoft Windows do not support 16-bit programs. As such, StatCalc will not natively work with the 64-bit versions of Windows.
Some of our users have had success running StatCalc on the 64-bit versions of Windows using a program called DosBox. See http://www.dosbox.com.
Additionally, OpenEpi provides much the same functionality as StatCalc and is available for free. See http://www.openepi.com.