hi again! what mcu are you using?
in "the i2c pins and jtag pins are multiplexed" do you mean the i2c and jtag are in same pin? Isn't there a way to select just one of them to function? (in Zds, some pins perform multiple function and you select what you want by setting the alternate function) I'm not sure if yours work that way.
anyway, if you want to connect to your computer, i think, you have to access the uart of the mcu. you can print the data to hyperterminal from the i2c using uart. the i2c code that you will need depends on the device that you are interfacing via i2c. hope that helps.