The installer automatically creates a folder in:
Common\Plug-ins\CS5\MediaCore
Common\Plug-ins\CS4\MediaCore
Common\Plug-ins\CS3\MediaCore
Just delete the folders
If it’s an old installer, it might be in the application Plug-ins folder
example: Adobe After Effects CS5\Support Files\Plug-ins
That’s the only two places AE looks for. If it’s not on your disk it won’t load any plugins.
Pierre