Two days ago my laptop with XP SP3 started having problems on some websites requiring the latest version of Reader (I already have 9 installed). IE7 would hang or crash, requiring me to ctrl-alt-del to force the program to quit. So I uninstalled, then reinstalled Reader 9. That didn't fix the problem, so I decided to roll back to an earlier date using System Restore (as the problem started only a couple of days ago). The problem wasn't resolved, so I thought that by rolling back I may have affected the installation of Reader 9. So now I try to uninstall it but get the following message: "This patch package could not be opened. Verify that the patch exists and that you can access it, or contact the application vendor to verify that this is a valid Windows Installer patch package". I open Reader, then Repair Adobe Reader Installation in Help. I briefly get a window saying "Preparing to Install" but nothing happens. I also reinstalled IE7 with no effect.
Having said all this I also have Acrobat Standard 6 installed. It did not have all the updates installed at the time (but now does). Before the recent problem started, I noticed that a few websites I opened would give the message: "The Adobe Acrobat/Reader that is running can not be used to view PDF files in a web browser. Adobe Acrobat/Reader version 8 or 9 is required. Please exit and try again." I click OK or close the box and Acrobat Standard starts.
It's interesting that the website I now have the most problems with is Adobe.com. The Flash animations don't appear, and I coudn't get to the Forum I needed without IE hanging. (I had to send this from another machine.)
Any help welcome...all other apps seem ok.
Problem solved. Used Windows Install clean-up on Reader 9 files, then uninstalled Flash and Acrobat Standard 6, installed IE8 and Reader 9.0 (from files already in desktop folder). Then upgraded to 9.1. What a pain, but it works now.