Adobe makes a good job of promoting its new version of their Flash Player 10. They seem to have removed almost every single link to the previous version on their website and all old links redirect to the download of version 10.
This might be great if you want to run their latest software, but if for some reason you need a specific older version, you’re gonna be quite upset, e.g., you want Flash on a legacy operating system such as Windows 98/ME, Mac OS X < 10.4, or older Linux/UNIX OSes.
In my case, there is a web site that has been programmed in such a bad way that it is simply broken and unusuable with the latest version of Flash Player 10. I don’t use the service of that website on a daily basis, but I wanted to install Flash Player 9 on top of a Windows installation in a VM.
You can find the installation files for the legacy Flash Player 9 download on Adobe’s TechNote site. Please keep in mind that Adobe may (and surely will) stop releasing any [security] updates for those old versions of Flash.
Of course–after I eventually found the download link and installed the old Flash version–I remembered having a moldy Ubuntu Live DVD somewhere in my drawer… And I bet it has Flash Player 8 or 9 installed…