Messaging

I have a mac and my friend has a pc. we would like to be able to do video/audio chat. I have seen skype and we are going to try it out. but what we really wanted was to be able to use our msn accounts to do the video/audio chat. my friend has msn messenger 7.5 and that lets you use a webcam etc... but I have seen nothing for the mac. I have tried aMSN and Mercury but they don't let you do audio chat with a webcam. I have an isight and know that it has a built in microphone so it must be possble somehow. please help me!!!