3rd party apps

[Chezer01]

Hello,
I have enabled the tab in settings -> security for installing apps from unknown sources. Yet when I get to the install screen, the install button still does not work. I have turned this tab off and on many times still with the same effect.
I am at a loss how to install 3rd party apps. Am I missing something?
Thanks for replies in advance
Chezer

[Archanos]

You can't install any app incompatible with your device regardless of this setting.

Contact the app developer and ask if it is compatible with your phone at all.