Uninstall both versions of Acrobat, then reinstall only Acrobat 9 when you're done with that.
Otherwise, I'd say for the price Adobe charges for most of their software, they're obligated to send someone over to your house to fix it for you. At the very least, they can give you some email based support for issues like this.
I have adobe acrobat 9, and I had adobe acrobat 8.1, but still I can not open pdf files. They open up, but then it freezes and I get a message to install Adobe 8 Professional. Why would it not open those files up when I have Adobe acrobat 9. I didn't have this problem in my old compaq laptop. But I have not ben able to view pdf files since I bought Sony laptop.