[Typo3-debian] Installation

[Dietmar Fuhrmann]

I´m sorry but i have  to annoy you again.

After all my problems with my old installation i have made a new one with php4, mysql and all typo3-pakages. if i now put my 
URL on it, i get instead of the installation screen an index of/ Site. If i try to open the index.php i get the downloadbox. Has 
somebody an idea what is going wrong? 
(P.S.: the FollowSymLinks are enabled) 
Thank you