How do I set up a static IP for Port forwarding?

Outdated content This page does not reflect the current state of things. Some information within this article is either obsolete, hasn't been updated in a long time, incomplete, or otherwise invalid.

This is not needed for Allegiance anymore, but kept here as help for problems with other software.

Since one often needs to use static IPs for port forwarding to work, here is a link to a page, where you can find a guide for all the different Windows versions.