Vista - Default Mail Client

For reasons that are far beyond me, Outlook cannot seem to be configured to receive/send messages from my gmail account. I have put in the correct information but it just doesn't work. It also seems that I can't reset my mail client to be gmail which I have no trouble with. Is there to change my default mail client to gmail rather than outlook? I am spending too much time screwing around to get emails sent when Vista automatically opens up Outlook. Thanks.