It sounds like you updated joomla from a 1.5 website to a newer version but didn't reinstall HikaShop, or you did but you have access right issues in your modules folder which prevented joomla to update the XML files. Because of that Joomla cannot find the XML files as the structure for them is different since 1.6:
docs.joomla.org/What's_new_in_Joomla_1.6#XML_Manifest_Changes
The simplest is to edit the xml files in modules/mod_hikashop, modules/mod_hikashop_cart, etc with a text editor via FTP and change <install and </install to <extension and </extension and joomla should then be able to find them.
HIKASHOP ESSENTIAL 60€The basic version. With the main features for a little shop.
HIKAMARKETAdd-on Create a multivendor platform. Enable many vendors on your website.
HIKASERIALAdd-on Sale e-tickets, vouchers, gift certificates, serial numbers and more!
MARKETPLACEPlugins, modules and other kinds of integrations for HikaShop
