Deployment packages for applications may be created automatically to deploy unique instances of an application for execution on a computer system. The deployment packages may be created by copying an original deployment package to a new deployment package and modifying properties, attributes, and/or values within the new deployment package. The modified parameters may include a globally-unique identifier (GUID). The modifications to the new deployment package may be performed automatically without access to source code for the application in the original deployment package. The new deployment package may be deployed on a computer system to install a unique instance of the application. Automatic creation of deployment packages may be useful for testing multiple copies of an application in parallel on a computer system.