Server Requirements:
Any issues involving the installation of this software are always tied to server settings or the server does not meet the requirements listed below. Many hosting companies continue to restrict accounts in an effort to reduce customer service. It is highly recommended you check your server settings prior to attempting an installation. Our technical department is willing to assist on any installation questions you may have, but we do charge 30.00 USD /hour for issues that are not associated with the software and are deemed to be server-setting issues. If you are not sure if your server supports the below requirements, take the time to send in a request to your hosting company to verify prior to installation.Required

PHP 5.x or higher
MySQL 3.2 and above
Apache Web Server (http, https)
90 MB of free disk space
GD Library Support (version 2 recommended)
cURL Library Support
ZLib Support
Ioncube Loaders version 4
Joomla 1.5 or 1.7 preinstalled 

Joomla 1.5x & 1.7x Installation:
First you will need to unzip the ZIP folder that contains the IXXO Multi-Vendor for Joomla 1.5-1.7  Package.
Folders included in zip:

installer
modules
upload
upload-2

Before installing the com_ixxocart.zip component, make sure that the tmp folder in your joomla root directory, has attributes set to 777 or 755 depending on your server. If not change to either 777 or 755.
Also check if your server's safe_mode is turned off. If its on you should change to off. This is required for some server environments.
The installer folder contains the IXXO Cart Multi-Vendor Component for Joomla 1.5 - 1.7, that needs to be installed first.

   1.  Login to your Joomla installation
   2.  Click on the extensions tab and click on the "install/uninstall" link
   3.  In the new window click on the browse button and choose the com_ixxocart_353.zip and press ok.
   4.  Click on Upload File & Install button
   5.  If you did everything right you will get a message "Upload Component - Success"
   6.  Select from the "Components" drop down Menu the "IXXO Cart" link
   DONT CHANGE THE SCREEN UNTIL YOU UPLOAD the 2 ZIP FILES included in the "upload" folder, TO THE SERVER 
   7.  Now you will need to manually upload the the 2 zip files with your ftp client.
   8. Upload the 2 zip filess to: /administrator/components/com_ixxocart/

   9.  Set the following folder attributes to 777 or 755
      "com_ixxocart" in administrator/components
      "com_ixxocart" in components/

10. GO back to your browser and click on "click here" to continue the installation

12. After the cart has been installed, Change the attributes of the "compiled" folder in /components/com_ixxocart/content/ to 777 or 755.

13. Now you will need to manually upload the five files included in the "upload-2" folder to your joomla installation root directory.

After successful installation you will need to install the modules found in the "modules" folder like you do with any other joomla module.

According to your template module positions you will have to choose the right position  for each module to be displayed.

It's not necessary to publish all of them if not required.