Nokia consumers report the Nokia 5800 Express Music phones with touch screen got a software bug in installation software. This bug prevents you from installing any Symbian signed or developer singed sis packages with applications. You always got "Expired certificate" error message. For self-signed applications installation process finished successfully. This happens probably because of newSymbian S60 5th Edition software running on Nokia 5800. On some user forums people find a solution to solve this issue.The main action you have to do is to reset your phone's software to manufacturer state via key sequence *#7370#. Device ask you to enter lock code, it should be 12345. But you can backup all your data before this action with Nokia PC Suite and restore it after resetting software.Also it's better to update phone's firmware to latest version (to check version number press *#0000#) because in older versions you may still got "Expired certificate" error message sometimes later.
That's it! Now you can install any application you want, even developed for older S60 3rd Edition devices like Fring, Google Maps, Mobiola, etc.
