Do a Custom installation to a uniquely named Program Files folder, like /Program Files/Firefox-4.0/ .

Then create a new profile exclusively for the 4.0 beta version and create a desktop shortcut with -P "profile" appended to the target to launch that profile.

• http://kb.mozillazine.org/Testing_pre-release_versions

• http://kb.mozillazine.org/Creating_a_new_Firefox_profile_on_Windows
• http://kb.mozillazine.org/Shortcut_to_a_specific_profile
• http://kb.mozillazine.org/Using_multiple_profiles_-_Firefox

You can install them both but there are a few steps to take.

When you install Firefox 4 use the custom installation option and choose a different location to install Firefox.

In order to use both versions, you need to create a new profile for Firefox 4 (Firefox stores user data in the profile). Using the same profile with different versions can cause problems. Once you create a new profile you can copy certain data such as bookmarks and passwords between them. You can also use Firefox Sync to keep the profile synchronized. Finally, you will need to set up shortcuts to launch the correct profile for each version.

The following links show how to do this:

• http://kb.mozillazine.org/Creating_a_new_Firefox_profile_on_Windows
• http://kb.mozillazine.org/Shortcut_to_a_specific_profile
• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox
• https://addons.mozilla.org/firefox/addon/firefox-sync (only needed for Firefox 3.6, it is built into Firefox 4)

Do I need to use a custom folder for the new profile?

When you create a new profile using the method shown in the links above, use the default location for storing profiles, do not use the "Choose folder" option.

I have tried several times to install Firefox 4 in separate folder, but the installation replaces all the other versions of Firefox wherever they are. I have also created another Profile but this doesn't make any difference.

Any other suggestions please?