The AquaCalc 5000 and the older discontinued AquaCalc Pro (replaced by the AquaCalc Pro Plus which has a USB connection built in) use a serial RS232 Connection with a DB9 connector. These connection are no longer available on many laptops, but a USB to Serial RS232 adapeter can be used in Windows so that the AquaCalc DataLink can be used to download these units.
The FTDI chipset USB to RS232 serial adapter can be found here:
Tera Grand - Premium USB 2.0 to RS232 Serial DB9 Adapter - Supports Windows 10, 8, 7, Vista, XP, 2000, 98, Linux and Mac - Built with FTDI Chipset
Using a USB to Serial RS232 Adapter