Please do the following.

Go to Download Firefox v3.6.17 and download it to the desktop.

Then go to Add/Remove Programs, scroll down to Mozilla Firefox and remove it, choosing to keep your bookmarks, customizations etc., (don't checkmark the box).

Then reboot and delete the folder called Mozilla Firefox at this location: C:\Program Files\Mozilla Firefox

Finally run the installation file you downloaded to the desktop earlier.

Your bookmarks, customizations etc., are maintained in a different location and will become available to you again once you complete the installation.

After you complete the installation, go to the Plugins Check page and update those where necessary.

The skin may never be made compatible.

To downgrade to Firefox 3.6 first uninstall Firefox 4, but do not select the option to "Remove my Firefox personal data". If you select that option it will delete your bookmarks, passwords and other user data.

You can then install the latest version of Firefox 3.6 available from http://www.mozilla.com/en-US/firefox/all-older.html - it will automatically use your current bookmarks, passwords etc.

To avoid possible problems with downgrading, I recommend going to your profile folder and deleting the following files if they exist - extensions.cache, extensions.rdf, extensions.ini, extensions.sqlite and localstore.rdf. Deleting these files will force Firefox to rebuild the list of installed extensions, checking their compatibility, and reset toolbar customizations.

For details of how to find your profile folder see https://support.mozilla.com/kb/Profiles

thanks guys!... i was impatient and googled "firefox versions" and found pretty much the same answer and link to a mozilla page... funny how google is able to find something on the firefox site that mozilla doesn't make readily apparent...

You're welcome.

Oh, and yes, the Moz search utility does leave a lot to be desired. :(

I have upgraded to FF4 and now I cannot open it. I get an error message saying 'Entry point not found' ....... could not be located in the dynamic link library MOZCPP19.dll. When go to uninstall it is showing version 3.6.16. Can anyone help please?

i didn't even think to use the mozilla search... i demand that links be made highly visible to me that specifically address my needs!...

not too much to ask, is it?...

How did you upgrade? via Help | Check For Updates, or did you download the installation file from somewhere?