Adding this add-on Rated 5 out of 5 stars

Hello all. I need a bit of help. I'm trying to install the official Bing search add-on v20090601 in to Google toolbar for FF. The toolbar is v7.1.20100408Wb1 with FF v3.6.3. The error message that I get when trying to install the add-on is as follows:

Firefox could not install the search plug-in from "https://addons.mozilla.org/en-US/firefox/downloads/latest/10434/addon-10434-latest.xml?src=addondetail" because an engine with the same name already exists.

I don't have and didn't have the Bing engine installed. I did before, but it was in earlier versions of FF. When I updated to FF V3.6.3, it, the Bing search add-on, seemed to have disappeared which is why I'm trying to reinstall it. I uninstalled the Google toolbar for FF and updated to its latest version. Prior to that, I attempted to add the add-on to the previous toolbar v6.* without any success. I'd even tried adding the add-on using the "Make Bing your decision engine" link via the actual Bing homepage, but got the same error message.

Through a bit of diligent troubleshooting, I kinda' realized, but yet fully solved the issue. I ran FF as an admin- both normally and in safe mode-and found that it was installed there. So I uninstalled from both then reinstalled it in FF as a standard user. I no longer got the error message, but it still didn't appear while FF is running normally. I then ran FF in safe-mode, with normal privileges, and the add-on did appear in the toolbar. (I, of course, uninstalled it because I don't wanna' have to run FF with elevated privileges nor in safe.) So the question now is how do I get the add-on to appear without running FF with admin privileges?

Windows Vista Home Premium SP2