I've searched the help pages and FAQs and I can't find an answer to this.
Acrobat Reader 8.? started misbehaving - not opening docs, or saying it couldn't then doing it anyway, then refusing to open a second one, and hanging the machine.
So - decided to install latest version. Downloaded 9. 9 refused to install. Removed all traces I could find (via Add/Remove Programs) of previous versions. Still refused to install.
In desperation, manually removed al traces of software in program files, edited registry to remomve all traces and references. STILL refuses to install. (It does however manage to install something called acrobat.com and Adobe AIR - whatever those are - but neither of which I asked for or want"! THEN it stops!)
Screen shot of error message(s) at: http://www.stephenbell.net/images2/screenshot.jpg - always the same.
The first time I got that error there WAS no previous version of 9 on the system - 8 yes, 9 no. Heeeeelp! :-)