It almost seems more worth your time to buy a development board. The easiest thing I could think to do would require that you have two COM ports and a serial crossover cable.
You could write a small program in the language of your choice (C,C#,Java,VB, whatever). That could pull data from a file (output from your simulation) and send it out one COM port. It could also listen on the COM port and route any incoming data to a file (input to your simulation).
On the other COM port of course you have Hyperterminal.
However, I don't really see the benefit of doing this unless your are trying to test Hyperterminal. You could just as easily write a task in your simulation to provide the data and print out the data to/from your simulated COM port.
Perhaps someone else has a better idea.
Jake