All it means is you have to close Firefox then re-open it. In the File menu select Exit, then click on the Firefox shortcut to re-open it.

If you keep on getting this message to restart Firefox to complete the installation of an add-on, one of the files that stores details of installed add-ons may be corrupt. to fix that follow the instructions for "Corrupt extension files" in the Unable to install add-ons (extensions or themes) article.

Your above posted system details show outdated plugin(s) with known security and stability risks that you should update.

• Java Plug-in 1.6.0_06 for Netscape Navigator (DLL Helper)

Update the Java plugin to the latest version.

• http://www.oracle.com/technetwork/java/javase/downloads/index.html (Java Platform: Download JRE)

Update the Adobe Reader plugin to the latest version.

• http://get.adobe.com/reader/otherversions/