OK I tried once more and this is what the error says now - is there anybody who knows how to fix this one? I really wanted to use this software but it is getting too difficult to install:

Installing SilverStripe...

I am now running through the installation steps (this should take about 30 seconds)

If you receive a fatal error, refresh this page to continue the installation

* Creating 'mysite/_config.php'...
* Creating /home/content/b/o/n/bonjour089/html/underground/mysite/_config.php
* Creating '.htaccess' file...
* Creating /home/content/b/o/n/bonjour089/html/underground/.htaccess
* Building database schema...
* Checking that friendly URLs work...
* Friendly URLs are not working. This is most likely because mod_rewrite isn't configuredcorrectly on your site. Please check the following things in your Apache configuration; you may need to get your web host or server administrator to do this for you:
o mod_rewrite is enabled
o AllowOverride All is set for your directory

SOLVED: mod_rewrite Issues

ISSUE: During installation the .htaccess file gets written to the "wrong" directory. It puts the .htaccess file in the SilverStripe-v directory after unpacking and doing a browser install. Remove the .htaccess file from the SilverStripe-v dir and place it in the root, problem solved. This is the correct code for .htaccess:

### SILVERSTRIPE START ###
<Files *.ss>
   Order deny,allow
   Deny from all
   Allow from 127.0.0.1
</Files>

<Files web.config>
   Order deny,allow
   Deny from all
</Files>

ErrorDocument 404 /assets/error-404.html
ErrorDocument 500 /assets/error-500.html

<IfModule mod_alias.c>
   RedirectMatch 403 /silverstripe-cache(/|$)
</IfModule>

<IfModule mod_rewrite.c>
   SetEnv HTTP_MOD_REWRITE On
   RewriteEngine On
   RewriteBase /

   RewriteCond %{REQUEST_URI} ^(.*)$
   RewriteCond %{REQUEST_FILENAME} !-f
   RewriteRule .* sapphire/main.php?url=%1&%{QUERY_STRING} [L]
</IfModule>
### SILVERSTRIPE END ###