If you find that OziExplorerCE cannot report speeds <5km per hour, the problem is that the GPS has Static Navigation turned ON.
This is a setting in the SIRF III GPS Receivers called "Static Navigation". It is possible to turn Static Navigation OFF. Some PDA's already have an option to do this but others do not. In this case there are several utilities available on the internet which allow you to turn off Static Navigation.
The aplsirf program works well, copy the program to your PDA and run it.
The SirfTech program works well.