I assume that you have OS X 10.6.7 and not 4.6.7 (Snow Leopard is OS X 10.6)

• Download a new copy of the Firefox program
• Firefox 4.0: http://www.mozilla.com/en-US/firefox/all.html

• Trash the current Firefox application to do a clean (re-)install
• Install the new version that you have downloaded

Your profile data is stored elsewhere in the Firefox Profile Folder, so you won't lose your bookmarks and other personal data.

You didn't answer my question. I have a Mac and my operating system is snow leopard 10.6.7.....sorry about the error in my initial message. When I download Firefox 4.0 I get an installer that when I click on the installer I get an icon on my desktop. To put Firefox in my applications I drag the icon to the Applications file. It then does a strange thing and that is it duplicates my Applications file. I put the Firefox icon on my dock and try to put the desktop application in the trash and then the dock icon won't work. How can I eliminate the Firefox icon from my desktop, and how can I eliminate the duplicated application file when Firefox is in the applications folder?

Make sure that Firefox gets installed properly.
Open the DMG file and drag to Firefox program to the application folder on your hard drive.
You shouldn't double-click the Firefox application to run it from the disk image, but drag it out of the DMG folder instead.

• How to download and install Firefox on Mac
• http://kb.mozillazine.org/Installing_Firefox#Mac_OS_X