Rated 4 out of 5 stars
I've got this addon working. I used the "fixed" version but I assume it will work with this version if you can download it. I first used FEBE to backup my addons and I then used a ZIP program to unzip the Googlebar XPI. Then I used Notepad to look at the Install.rdf file. Look for these lines:
<!-- Firefox -->
Look in Firefox Help/ About Firefox menu to see the what your version of Firefox is and change the max version to that. You'll have to do that for every new version of Firefox unless the author updates the addon. Now you have to type about:config into the address bar. Now type in xpinstall into search box. Now look for xpinstall.signatures.required. Double click on it which will change it to false. Now go to Add-ons in the Tools menu. Click on the gear icon menu then click on Install addon from file and search for the location that you specified for your FEBE backup and install Googlebar. Now your set.