1. A method for patching a virtualized application, comprising: storing a current version of a virtual application image that is segmented into blocks and captures setup-time changes and run-time changes made to a client computing device by the virtualized application at a first location; accessing a current mapping file from the first location for the current version of the virtual application image that is a separate file from the virtual application image and comprises a number of blocks in the virtual application image and a location of each block in the virtual application image; determining on the client computing device changes to a client virtual application image by comparing the current mapping file to a client mapping file, wherein the client mapping file comprises a number of blocks in the client virtual application image and a location of each block in the client virtual application image; obtaining essential blocks from the virtual application image from the first location when the client computing device is executing the virtualized application in a network mode, wherein the blocks that are marked as essential for execution are downloaded; obtaining the changes from the current version of the virtual application image at the first location; and updating a client version of the client virtual application image using the obtained changes and any portion of the client virtual application image that did not change.