Thanks! Something to consider when I'm feeling confident. Normally when I try anything at all involved I end up having to do a clean install as I screw something up
As long as you place that portable version in a folder by itself... (I have mine in a PortableApps folder under my name) and it will never touch your installed version.
Also... I've always made backups of my profile prior to making any major changes to it or just prior to updating Firefox...
Profile backup - MozillaZine Knowledge Base