I would get to 99.99% and watch the installer close.
The following steps worked for me, YMMV.
DISCLAIMER! I make no warranty this will work for you! Follow these steps at your own peril and don't complain to me if your computer melts down or if you experience any of the following:
your dog runs away
your significant other runs away
meteor strikes to your barn
Uninstall all previous versions of reader.
Open Regedit and search for "ADOBE".
Delete all keys that you find. I found at least three.
Grab the following file from Adobe's ftp site. AdbeRdr90_en_US_Std.exe This version is the standard, no AIR/ADOBE.COM installer. I don't know what the StdA or StdE versions are, nor do I particularly care. The Std one worked for me.