Virtuemart is not a standalone system. It needs to get installed over content management system such as Joomla or Mambo. Virtuemart earlier called as PHP Shop as been one of the most important components of Joomla and mambo since the birth of these systems. While it is available since a long period virtuemart has been quite considerate using maximum possible environments to get it work so is Joomla. Virtuemart's requirements are same as Joomla and nothing extra is
Magento is based on LAMP which stands a short form for Linux Apache MySQL and PHP. At point it may worked for WAMP which replaces Linux with windows but its not recommended. As a language platform Magento looks for PHP 5.2 and above and won’t settle below that. If your host is running older versions of PHP then you should double check. Industry standard hosting such as 1and1 have both PHP4 and PHP5 available on the servers however it needs a little
CS cart isn't environment hungry script and doesn't demand much of specifics on Linux boxes. It runs pretty well with shared hosting as well dedicated and relatively easy to handle in small hosting companies too. Based on LAMP it's always advised to host CS cart on Linux platform. Oddly enough CS cart can work on Windows too however it will be little tricky to get it working in right order because of some file permissions and secondly it wont be as secure as it will on Linux.