I am using a Presentation Software other than E-Prime / SuperLab - can I still use it with a PowerLab and LabChart?

It is possible for any Presentation Software to interface to an ADInstruments PowerLab's Digital Input, providing it is able to write events / information to the Parallel Port (sometimes referred to as the Printer Port) of the machine running the Presentation Software.
Assuming the software meets the above criteria, you then simply need to connect an E-Prime Interface Cable between your machine's Parallel Port and your PowerLab's Digital Input.
Information on whether the Presentation Software is able to write to the Parallel Port, as well as how to configure this, should be found in your Presentation Software's User Guide.