The original version that was available was a SVN development version with full version control so 80% of the files were redundant for a normal user. The slim version is without the SVN files. That link was from September, they have released several versions since then, you should check their site for the latest download.

Magento isn't the easiest script to install and the sever requirements are quite strict. PHP5, Apache with mod_rewrite, mcrypt, Zend Framework etc, etc Have you checked the server requirements on their site?

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Lawrence