Don't use the DNS thing by Microsoft. Use ZoneEdit. With ZoneEdit, you can have up to 5 free domain DNS entries, and it's very easy to set up. Once you set up the DNS, it should direct the domain to your IP address.
ZoneEdit's website is
http://www.zoneedit.com
And to the mods, THIS POST is NOT an advertisement for Zone Edit, nor am I in any way affiliated. I am just a satisfied customer.