I'm sure your 5 year old laptop can handle broadcasting audio. The appeal of the experiment is hearing what you and callers have to say. I'm sure an audio format could work as a temporary solution.
I'd say Ustream is the best choice if you want to catch the attention of people that already follow you on there. I'd also do an mp3 recording that you can throw into RSS somewhere so that people can subscribe to a podcast style feed on itunes or wherever they currently listen to podcasts.