Making and receiving Telephone calls through MS Outlook

I bought a headset with a microphone. I want to use the headset with MS
Outlook to make phone calls. I am able to make a phone call in Contacts but i
keep getting cut off with an error messge stating the "Call annot be
completed a dailed". The modem seems to be working fine. Also, I can't answer
incoming calls. I can't find the information in need int he Help menu. What
do I need to do to setup my computer to send and receive calls through MS
Outlook?
Thanks,