Showing plug-ins window on different computer

Hello,
I have a number of extensions installed and all work o/k.
When I launch FFP on a different computer, the plug-ins window pops up with all the extensions shows and a line near the top saying that 1 new extension has been installed.

I have deleted extensions.ini, extensions.rdf and extensions.cache. These get re-created next time FFP is launched, But when take the USB dribe to another computer and launch FFP there, the plug-ins window pops up again.
Than you for any suggestions.