Adobe Reader update installation error

Hi,
I was using the Acrobat Reader 9.4.2 on my Windows operating system. But yesterday a message pop upped for the update of the reader. I updated the files, but when I tried to install the files it failed. A message was displayed showing “Error code 1646”.
I tried numerous times looking for a solution online but could not find the answer. Tell me if you can help me with this. Thanks.
