Quick start installation problem

Hi,

When I start to install I am receiving the following dialog:

Warning: strpos() [function.strpos]: Empty delimiter in /libraries/joomla/filesystem/path.php on line 156

I found how to fix it and made the following change:

in the file: /libraries/joomla/filesystem/path.php

I made the change:
if (strpos($path, JPath::clean(JPATH_ROOT)) !== 0)
to:
if (strpos($path, JPath::clean('/')) !== 0)

Installator worked smoothly but then after removing installation files the backend is not available after login (the page doesn't exist) and most of the pages on frontend as well (only homepage is ok).

the address of the site b.softelligence.pl
hosted on Home.pl

Please advise how to proceed...

I replied you at https://www.gavick.com/support/forums/7/12550.html