I'm convinced that trying to download and install an update over the older
version can lead to corruption of the install producing any number of error
messages and non-functioning of the program or failure of the new install and
corruption of the older version as well.
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 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. AdobeFlash, 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 it’s finished, Smarty UI identifies any
program remnants and will then uninstall the remnants (from files and folders
to registry entries). For Smarty UI (free trial period) or alternative
uninstaller Revo (free) see links below:
http://www.winnertweak.com/uninstaller/
http://www.revouninstaller.com/
After running the uninstaller program of your choice I recommend using the
Windows Installer Cleanup Utility to finish off the uninstallation. This
program is available at the following link:
http://support.microsoft.com/default.aspx?scid=kb;en-us;290301
Once the program you're interested in is completely uninstalled, you can
then do a clean install of the new version without problems. Download Adobe
Reader without the Download Manager from this site:
ftp://ftp.adobe.com/pub/adobe/reader/win/8.x/8.1/enu/AdbeRdr810_en_US.exe
If all this fails, you can do a clean reinstall of your OS or switch to
another PDF reader like Foxit:
http://www.foxitsoftware.com/