Mostly this problem arises because you have not unpacked the file VirtueMart_x.x_COMPLETE_PACKAGE.zip before and tried uploading / installing this file.

The most common reason for this problem is that the File you have uploaded is too big. The File Size Upload Limit on your Server is set too low to allow larger files to be uploaded. By default PHP allows files up to 2 MB, but this limit needs to be set to 4 MB in order to upload the VirtueMart Component Install File.

If you have access to the php.ini, then change the directive upload_max_filesize to "4M" and reload the server configuration.

If you are running PHP in CGI mode on Apache, you can place an .htaccess file in your Joomla! root directory and place the following code inside:

php_value upload_max_filesize 4M

You have probably uploaded an old Version of VirtueMart or an old Module, which is not ready for Joomla! 1.5. Make sure you have downloaded the Virtuemart Package for Joomla! 1.5 (with the file extension ".j15.zip").

VirtueMart 1.0.x is not compatible to Joomla! 1.5 and no efforts are taken to achieve compatibility.

Please delete the directories /site_root/components/com_virtuemart and /site_root/administrator/components/com_virtuemart. If you can't delete the directories using ftp, try the file manager for Joomla!, eXtplorer, instead.

VirtueMart is a big component, its installer file archive has a size of more than 2 MB. When uploading this file to your server you can wait a long time until the file is completely transferred to your server. You can use the Remote Installer for VirtueMart instead! (Remote Installer for VirtueMart)

tar.gz Archives come from the Unix World, but they can be used on Windows and Mac systems as well. On Windows you can unpack them using Winzip or Winrar. Gzip has a much much better compression than Zip, that's one reason why most Open Source projects use it for their distributions.

Sometimes the tables beginning with jos_pshop_ or mos_pshop_ are not found. Before you click on "Install sample data" or "Go directly to the shop" you can just type in this URL in the addess bar of your browser:

index2.php?option=com_virtuemart&install_type=update12pl3

After that the upgrade procedure begins!

The installation is corrupt. The registered functions and core modules, which are used by VirtueMart to check the acccess permissions are missing. You need to make sure that the tables "jos_vm_functions" and "jos_vm_modules" have been created in your database and contain records. If they are missing, you can add those tables manually by using the SQL installer file /sql/virtuemart.installation.joomla.sql. Search for those tables, copy the SQL code and paste it into the textarea in phpMyAdmin's SQL execution screen.

VirtueMart is no component-only script. It's programmed to be used together with the corresponding VirtueMart Main Module. VirtueMart will not operate properly without the VirtueMart Main Module.