Bruce,
You can add it as part of your IIS installation using the Control
Panel | Add/Remove Programs | Add/Remove Windows Components then select the
IIS node and click the Details button. You should see an option for SMTP
Service. You don't need a dedicated domain name for the SMTP since all it
does is relay to somewhere else.
I'll be frank though, trying to host on a home system is really not
a good idea. One, you're opening up your internal network as well as your
computer to possible viruses, trojans, attacks, etc. simply because the
computer has to be opened to the internet. Most home users just don't have
the security expertise to keep their computers threat-free when they open
them up like this.
Windows XP and all MS non-server OSes are limited to 10 simultaneous
connections. This does not mean 10 users, only 10 connections. One user
could use all 10 connections at once and thus lock anyone else from
accessing the web server (including you).
If you're on a broadband connection I would suggest you look at your
agreement. Most ISPs specifically prevent your from hosting web sites at
home. They don't want businesses running on residential lines so they
typically block access and attempting to circumvent it can be a breach of
contract and they can disconnect your service or force you to move to a
corporate account.
With professional hosting costing as little as $5 a month, it's not
worth it.
