IP reporting software for tracking stolen PC?

I am looking for a piece of software that will automatically run on startup and report its Comcast/Verizon/whatever IP address in an email. Really simple, should be some freeware out there to do it. I just cannot seem to find any except WAY overpriced laptop software.

The reason is to track down anyone who breaks in and steals my desktop. But the desktop is not the main concern. I have other items that are much more desirable to a criminal, and just hope they take the PC along with them if this ever happens.

Anyone got any ideas? Thanks!

 

Here is one:
http://adeona.cs.washington.edu/xpinstallguide.html

Iconico.com had locatepc but I think they quit offering it. The only issue with free programs, you never know when they'll quit offering the service & they don't have the support of the payware companies.