Why Do Programs Require Installation(Apple’s iTunes software )

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For example, Apple’s iTunes software installs to Crogram Files (x86)>iTunes by default.
In a simpler world, you could copy the iTunes folder to a new computer and run iTunes from the folder without any additional work. However, it isn’t this simple. Programs actually scatter their data all over the place:

• Registry Settings: Many programs save settings in the Windows registry. These settings may be scattered all over the Windows registry — for example, there may be several registry keys for program settings, other registry keys for context menu options, and keys that make the program the default program for certain files. If any of these registry keys aren’t present, the program may display errors when you try to run it.
• Other Program Folders: Certain programs also install other software that they require. For example, iTunes installs the Apple Application Support application, among others. If Apple Application Support isn’t present on your computer, iTunes won’t run. Apple Application support installs to its own folder and has its own registry settings, like any other program.
• Windows System Files: Some programs dump DLL files and other files into the Windows system directory and won’t run if these files aren’t present.
• System Services: Many programs install Windows services that they require. For example, Adobe Flash Player installs an Adobe Flash Player Update service. While you could copy the Adobe Flash plugin files to a new system, you wouldn’t have the update service and you’d have to manually update Adobe Flash. Installing Adobe Flash with the installer would ensure that the updater service is present. Some programs may not even run without these services available.
• Hardware Locking: A few programs may use DRM that ties the program to a specific computer’s hardware. They may refuse to run when you copy their files to a new computer.
• User Data Folders: Most modern programs don’t save their settings to their program folder. Whatever they don’t store in the registry is likely stored in each user’s Application Data folder. Even if you could copy the program’s files over, these settings would have to be copied or you’d lose your programs’ settings and data.
  

Theoretically, it would be possible to locate everything — registry settings, program files, system files, user data folders — and copy them to the new computer, reinstalling any system services and putting everything in the exact same place. However, this would be extremely tedious and would often require using some sort of program that monitors the changes an installer makes. In practice, simply reinstalling the program is much faster and easier. The installer will set up everything the program needs on your system.