1. A method for providing access to a file by a requestor comprising: creating an empty file representing a disk image in a format understood by the requestor, by; intercepting one or more reads by the requestor of said disk image; determining if a disk block of said empty file being read by the requestor should contain expected content, if said disk block of said empty file should contain expected content then, before fulfilling the read, adding said expected content to the disk image that would be stored in said disk block of said empty file to transform said empty file being read into a requested file; arranging to intercept reads for other disk blocks in the disk image that are referred to by the content of the disk block of said empty file being read; and fulfilling a read of said requested file.