Many of our users have asked us several times how to stop Google Toolbar from auto upgrading. I recently came across this unique tweak that will let you have version 3 and Google toolbar will not upgrade it in the future.

Stop Google toolbar autoupdate with HOSTS_FILE
Download and save to your computer Google Toolbar version 3 if you have already been generously updated to v4 without you permission OR knowledge, and you
no longer have the installer for your previous PREFERED version

http://www.oldapps.com/google_toolbar.htm (Old Versions of Google Toolbar)
Then, Uninstall your current (updated) toolbar using the google toolbar
help > uninstall OR Control Panel > Add/Remove Programs.
(MAKE SURE TO DO THIS BEFORE CONTINUING)
(if you have the time and can be bothered, tell them on the form that
their non-disableable autoupdate SUCKS - and anything else that comes
to mind)
Then go to http://www.oldapps.com/google_toolbar.htm and download version 3.
Find host file on your computer.
host file is usualy found in
c:\windows\system32\drivers\etc\hosts
Open it with a your editor (Notepad, Wordpad) and there will be at least one entry for
127.0.0.1 localhost
Add this line underneath..
127.0.0.1 toolbar.google.com
Save the file and (hopefully) no more updates until YOU decide you want
it - if and when you do, simply delete the toolbar.google.com line
again
(you will not be able to visit www.toolbar.google.com at all while this
is active...but why would you want to? lol)
To test - try visiting there, and you should just get "page can't be
displayed"
hope it works ok for you - it's been a number of days now and my
familiar v3 is still there the same... previously it would update
itself within hours (and a lot of times very quickly indeed) - so I am
optimistic this IS the one that will work permanently