OK - here's what I suggest to fix this issue:
1) download Microsoft's Windows Installer cleanup app from:
http://support.microsoft.com/default.aspx?scid=kb;en-us;290301
Use it to remove the installer entries for Acrobat Reader 6 from your
system.
Once this completes, then download and install version 7 from Adobe. It is
free, and doesn't contain spyware:
http://www.adobe.com/products/acrobat/alternate.html
I recommend installing 7 on Windows 2000, XP or Windows Server 2003 machines
because 6.x versions prior to 6.0.3 contain a security flaw. Version 7 does
not install on 9.x or Windows Millennium edition machines, however.
I believe that sequence will solve your issue and give you back the
capabilities of Adobe reader--let us know.