A diagnostic system and method for repairing computing devices comprises a diagnostic application running on a same computing system having a failed operating system (O/S). The diagnostic application is provided with access to the file system of the failed O/S image. The diagnostic software application collects relevant configuration information from the file system of the failed O/S image, and transports this information to a proxy system running the same operating system as the computing device being diagnosed. The proxy system utilizes the collected data to diagnose the subject failed O/S system. Once the proxy makes a determination it synthesizes repair information comprising new or modified files and instructions to be transported back to the diagnostic software system to apply. A network connection is provided between the computer running the diagnostic application and the proxy system that enables data to be easily transported between the two systems without human intervention.