I attempted to upgrade an Steel Beasts Pro install of some vintage to 3.027. However my attempts to upgrade the base program and switch have failed due to "mpir.dll not found. File must be available to run this application!"

How do I complete the installation successfully? Thank you in advance for your help.

Try the official SB web site lots of helpful advice there.

http://www.steelbeasts.com/sbforums/index.php

It may depend a bit on how exactly you tried to perform the upgrade. The Release Notes give a description of how to do it (e.g. in the case of 3.027, it's probably best to simply uninstall all previous versions before then applying the full installer. With a complete installation the missing "mpir.dll" shouldn't occur to begin with.

Release Notes and installers can be found on our Downloads page.