Joomla 1.5 problem

[modequipment85]

hi,
i'm new to web devepolment and i just installed joomla to my site(http://modequipment.x10.bz/)
But only the the first page works and any other page opens without any images on it.
(e.g. http://modequipment.x10.bz/index.php/about-us)

however, if i manually remove the "index.php" from the above URL, the page says 404 error
(http://modequipment.x10.bz/about-us)

please help with the issue.
thanks