ACR works w/ Google Toolbar IF... Rated 4 out of 5 stars

There are TWO files that need to be modified. If done right, the second change listed here in the file INSTALL.RDF will only need to be once per machine.

You must add extensions.checkCompatibility.13.0.1
NOTE -- the .1 in the FireFox version!! (This will need to be RE-done again with any update to FF)

(Go to this URL:) about:config
then, search for extensions.check
-- (Just so you can put the new one in the right section). Then right-click, and say Boolean --- and then paste this string:
-- and choose false.
You will have to restart FF for it to take effect.

PART TWO --- (only needs to be done once, per machine)

First FIND the file that is located HERE:

In XP:
C:\Documents and Settings\MY USERNAME\Application Data\Mozilla\Firefox\Profiles\c0m2y3zm.default\extensions\{3112ca9c-de6d-4884-a869-9855de68056c}\INSTALL.RDF

In WIN-7:
C:\Users\MY USERNAME\AppData\Roaming\Mozilla\Firefox\Profiles\kpd2i9xl.default\extensions\{3112ca9c-de6d-4884-a869-9855de68056c}\INSTALL.RDF

Edit the file, (right click and choose edit), and near the top, and CHANGE the maxVersion from whatever it is, to a "high number" I used 24.0.* since I think that should be sufficient for at least a year ;)) Note the star as perhaps optional. Also, read the note below about the MINversion if you are enabling another extension that isn't working, which suggests changing the minVersion as well.

< em:minVersion > 2.0 < em:minVersion >
< em:maxVersion > 24.0.< em:maxVersion > === Make this BIG

I'll repeat xTridence advice verbatim (given in an earlier post),

1. Go to %APPDATA%/Mozilla/Firefox/Profiles
2. Go to the folder ending with .default
3. Go to extensions
4. For example, Google Toolbar belongs to a folder (other plugins might be installed elsewhere). Look for install.rdf.
5. Look for &lt;em:maxversion&gt;
6. Change the max version supported to a higher number (preferably higher than the current version of Firefox)
7. Restart Firefox

Here's the MINversion advice, if needed, which was posted at: by Enigma (I didn't need this for Google toolbar to work)

Since “binary add-ons are never compatible *between releases*” (see, setting the maxVersion sometimes isn’t enough, but I just made two extensions compatible again by setting the maxVersion (to 10.*) *and* the minVersion (to 10.0).

NOTE -- I wonder who they are trying to protect?? We run ACR so we can run it ourselves and take the risks. (( Shameless Off-Topic political warning. )) Reminds me of the latest FDA rules mandating all beef to be served only well done and not rare, even if it sliced and diced steak and not hamburger. Maybe someday we can apply for a dare-devil license to do to things that are dangerous, or considered by some as too risky to allow me to try. Soon, we may need that license to cook or serve guests at home. We could even be accused of child abuse for serving rare steaks! -- Stop the madness please.! ))&lt;/em:maxversion&gt;

This review is for a previous version of the add-on (1.1.1-signed.1-signed).  This user has other reviews of this add-on.