impossible dacceder à l'admin apres installation

[clementine]

AU secours
mon installation s'est passée sans pb, repertoire install supprimé, mais quand je tape l URL de wwwmonsite/admin ( je n'ai pas rennommé le dossier admin ) j'ai :
Error 500 - Internal server error

Un problème inattendu est survenu.
Veuillez réessayer ultérieurement.
Je suis chez 1et1
help je ne sais plus quoi faire..
Pour info mon fichier htaccess :
##
# @version $Id: htaccess.txt 13415 2009-11-03 15:53:25Z ian $
# @package Joomla
# @copyright Copyright © 2005 - 2008 Open Source Matters. All rights reserved.
# @license http://www.gnu.org/copyleft/gpl.html GNU/GPL
# Joomla! is Free Software
##

AddType x-mapp-php5 .php .php3 .php4 .htm .html
AddType x-mapp-php5 .php
AddHandler x-mapp-php5 .php
#####################################################
# READ THIS COMPLETELY IF YOU CHOOSE TO USE THIS FILE
#
# The line just below this section: 'Options +FollowSymLinks' may cause problems
# with some server configurations. It is required for use of mod_rewrite, but may already
# be set by your server administrator in a way that dissallows changing it in
# your .htaccess file. If using it causes your server to error out, comment it out (add # to
# beginning of line), reload your site in your browser and test your sef url's. If they work,
# it has been set by your server administrator and you do not need it set here.
#
#####################################################

## Can be commented out if causes errors, see notes above.
Options +FollowSymLinks

#
# mod_rewrite in use

RewriteEngine On

########## Begin - Rewrite rules to block out some common exploits
## If you experience problems on your site block out the operations listed below
## This attempts to block the most common type of exploit `attempts` to Joomla!
#
## Deny access to extension xml files (uncomment out to activate)
#
#Order allow,deny
#Deny from all
#Satisfy all
#
## End of deny access to extension xml files
RewriteCond %{QUERY_STRING} mosConfig_[a-zA-Z_]{1,21}(=|\=) [OR]
# Block out any script trying to base64_encode crap to send via URL
RewriteCond %{QUERY_STRING} base64_encode.*\(.*\) [OR]
# Block out any script that includes a [removed] tag in URL
RewriteCond %{QUERY_STRING} (\<|<).*script.*(\>|>) [NC,OR]
# Block out any script trying to set a PHP GLOBALS variable via URL
RewriteCond %{QUERY_STRING} GLOBALS(=|\[|\%[0-9A-Z]{0,2}) [OR]
# Block out any script trying to modify a _REQUEST variable via URL
RewriteCond %{QUERY_STRING} _REQUEST(=|\[|\%[0-9A-Z]{0,2})
# Send all blocked request to homepage with 403 Forbidden error!
RewriteRule ^(.*)$ index.php [F,L]
#
########## End - Rewrite rules to block out some common exploits

# Uncomment following line if your webserver's URL
# is not directly related to physical file paths.
# Update Your Joomla! Directory (just / for root)

RewriteBase /


########## Begin - Joomla! core SEF Section
#
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_URI} !^/index.php
RewriteCond %{REQUEST_URI} (/|\.php|\.html|\.htm|\.feed|\.pdf|\.raw|/[^.]*)$ [NC]
RewriteRule (.*) index.php
RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization},L]
#
########## End - Joomla! core SEF Section

au secours svp !!!
merci a tous

[D-fox]

Joomla ? Vous n'êtes pas sur le bon forum ou votre installation est "mélangée" avec Joomla.