Instalation problem

kallosz

When I trying to install I get "500 internal ...".
When I refresh page

Garden has already been installed.
The error occurred on or near: /vanilla/v2/applications/garden/controllers/gardensetup.php
30: // Fatal error if Garden has already been installed.
31: $Config = Gdn::Factory(Gdn::AliasConfig);
32: $Installed = Gdn::Config('Garden.Installed') ? TRUE : FALSE;
33: if ($Installed)
34: trigger_error(ErrorMessage('Garden has already been installed.', 'GardenSetupController', 'Index'));
35:
36: if (!$this->_CheckPrerequisites()) {
37: $this->View = 'prerequisites';
38: $this->Render();