When I try to install an older build of Adobe Flash Player to test a SWF I'm developing, the installer tells me I cannot complete installation because a newer version of Flash Player is available. I need to install the older plugin because my users have reported that it exhibits different behavior than what I'm seeing with the latest update.
How do I install an older version of Flash Player to test?
In most cases, you can run the Adobe Flash Player uninstaller to remove Flash Player and its settings from your machine. After running the uninstaller, you should be able to install versions of Flash Player older than the one you most recently had installed.
If you're on Windows, and you still cannot install an older version of Flash Player after uninstalling, you may need to delete the some keys from the registry:
HKEY_LOCAL_MACHINE\SOFTWARE\Macromedia\FlashPlayer\SafeVersions
For more information, read the Adobe TechNote SafeVersions security restrictions prevent Flash Player installation.