In order to install a new or different version of an application type, often
the existing application or program has to be completely uninstalled first.
The Windows Vista Uninstall program is less than optimum at doing this and
frequently leaves remnant files and folders or registry entries of the
uninstalled program on your computer. Some software companies provide an
uninstall tool on their support website (i.e. Adobe, Norton, McAfee) which
can help with this process, but often even these special uninstaller tools
leave remnants of the program on your computer that can block or degrade the
installation of the new program. You can further clean up your computer
manually as outlined in the following tutorial:
http://www.vistax64.com/tutorials/87249-unable-install-latest-version-program-vista.html
I have since found and used a program called "Smarty Uninstaller" that does
an even better job of uninstalling programs, even tough ones like McAfee and
Norton. You scan your computer and the program identifies all the programs
on your computer, listing those that have their own uninstaller program and
those that are only remnants of a program. First you click for it to use the
program's uninstaller, and then when its finished, Smarty UI identifies any
program remnants and will then uninstall the remnants (from files and folders
to registry entries). Once the program you're interested in is completely
uninstalled, you can do a clean install of the update without problems. For
Smarty UI see link below:
http://www.winnertweak.com/uninstaller/