Manual installation/update of VM2

The manual installation of VM2 is quite easy. Just upload the files of the installation file so, that you have to merge the directories. Or in other words, copy the the directory /administrator/com_virtuemart to /administrator/com_virtuemart and so on. After that visit the view update Migration with the link /administrator/index.php?option=com_virtuemart&view=updatesmigration.

Choose there "Restore System Defaults" to install VM without sample data or take "Reset all tables and install sampledata" to install it with sample data.

To register VM2 in joomla use for j1.5
INSERT INTO `jos_components` (`id`, `name`, `link`, `menuid`, `parent`, `admin_menu_link`, `admin_menu_alt`, `option`, `ordering`, `admin_menu_img`, `iscore`, `params`, `enabled`) VALUES
(NULL, 'VirtueMart', 'option=com_virtuemart', 0, 0, 'option=com_virtuemart', 'VirtueMart', 'com_virtuemart', 0, '../components/com_virtuemart/assets/images/vmgeneral/menu_icon.png', 0, '', 1);

In j1.7 just use the discover feature.