The Excel file available below implements the same 2x2 game classification as the web program. The second worksheet also includes a graph of the payoffs and additional details. You must enable macros in the Excel file for it to work.
The .xml file available below contains the javascript code used to implement the web program. It is in an .xml file so that the javascript can be used in google sites as a gadget (added by URL).
A version written in C is available upon request.
A note on speed:
I'd always heard that Chrome is a faster browser than IE but had never seen that in practice until now. To see this, try changing the payoffs in the payoff matrix of the web program to u(C, C) = (2, 5); u(C, D) = (0,11); u(D, C) = (0, 12); u(D, D) = (1, -1000) in both browsers. I was quite surprised by the difference, taking under a second in Chrome and over 6 in IE.
EDIT: A few years later, this seems to no longer be the case, with IE finishing faster than Chrome.