Rental, installation and updating of computer software for cloud computing, namely, downloadable computer software for on-line access to databases of virtual machine images; rental, installation and updating of computer software being virtual machines and virtual machine images; providing an on-line database of virtual machine and virtual machine images; computer services relating to the provision of an on-line virtual machine exchange; providing a web site containing a database of virtual machine images, and/or location information for accessing virtual machine images; provision of information about virtual machines and virtual machine images via a web site