after first setup config I can't see website folder in HTDOCS

[giovacane]

My configuration: windows XP, apache server.

Follows what I did:
Copy zip folder in Apache htdocs
Extract zip folder. It creates the new folder named GetSimple_3.0
I open on my browser localhost/GetSimple_3.0
Correctly open the install page with the requirements: all requirements correctly installed
Click on "continue with setup"
Correctly open the setup page. Ask me for website name (testGetSimple), username (admin) and email (giovacane@ymail.com)
Click on "Install Now!"
Here the problem! Can't open "http://localhost/GetSimple_3.0/admin/welcome.php". it gives me "Internal Server Error"

By now, if I open localhost page on the browser I can't see the GetSimple_3.0 folder, that before the installation I could see.

I suspected an htaccess problem, so I delete the htaccess file in the GetSimple_3.0 folder, and now I can correctly access the website and the admin page.

I write here the content of that htaccess file:
/****START - THE CONTENT OF THE HTACCESS FILE********/
AddDefaultCharset UTF-8
Options -Indexes

# blocks direct access to the XML files - they hold all the data!
<Files ~ "\.xml$">
Order allow,deny
Deny from all
Satisfy All
</Files>
<Files sitemap.xml>
Order allow,deny
Allow from all
Satisfy All
</Files>

RewriteEngine on

# Usually it RewriteBase is just '/', but
# replace it with your subdirectory path
RewriteBase /GetSimple_3.0/

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule /?([A-Za-z0-9_-]+)/?$ index.php?id=$1 [QSA,L]
/****END - THE CONTENT OF THE HTACCESS FILE********/

Maybe I should change something in this file. I don't know.
What shoul I do?