[Typo3] Splash page while installing typo3

[Amir Mualem]

I am about to begin installing typo on my ROOT directory.  However I 
already have a site there, the one I am remaking.  I get many visitors 
to different parts of the site... how can I delete all the site files 
and pages, replace them with the typo3 files, and still keep one page as 
a notification of the redesign.

It would be the only page people see on the site until I finish redesigning.

Just like this site:

http://www.throughtheages.com/

Any ideas?