Application compatibility: During Windows OS Migration, a massive testing is required to validate the behaviors of existing software in the new version of OS. Also, many software would face a compatibility issue during migration. Hence you could package the software as portables and could port it to the new Version of OS, such as windows 7. Thereby, you can still use your applications as the same way in new Windows OS. You don't have to wait for an upgrade / support from your vendors. Most of the free software won't upgrade their wares to make them working on recent OS releases. Portable Apps solves this situation handy. Isolated Application: Packaged applications always run isolated from the operating system, that runs it. Package has its own registry and file system to read and write. As it is isolated, you can use 2 different versions of the same software on a same machine. Ensured System Security: With isolation principles, the packages would not affect the system registry and system files. This ensures security and integrity. Hence, you can even use the untrusted applications without any risk at your environment. To do that you have to package the application in a PC and can use the package in your environment.By the way, that does not alter your registry or file system environment. Application Portability: You can package it one time and can use anywhere. so your applications turns usable even from a USB / flash drive.