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In Windows 10/8/7 OS, by default, software gets installed on your System Drive, usually C drive, in the Program Files folder. The typical path is normally in Windows 32-bit is C:\Program Files and in Windows 64-bit is C:\Program Files and C:\Program Files(x86).
Microsoft recommends the C:\Program Files folder for the default installation destination. It's a convention that ensures proper inter-operation between your program and the OS's application and security models. So, once software programs are installed they go by default to C:\Program files on the computer.
This can, however, be changed by selecting another folder or location or partition. To change the default installation folder, the data must be modified in the ProgramFilesDir key and a new path must be chosen for the installation folder.
Windows uses the System Disk for installing any new applications, That is, if your Windows is installed on the C Drive, the default folder where all the applications you install would automatically show up as C:\Program Files, unless of course, you change in manually while installing the application's locations.
Do note that Microsoft does not support changing the location of the Program Files folder by modifying the ProgramFilesDir registry value. It states that if you change the location of the Program Files folder, you may experience problems with some Microsoft programs or with some software updates.
TIP: Windows 10 makes things easy. You can easily move Windows 10 Apps to another Drive and change its Install location.
Change default Program Files directory
If you almost always prefer to NOT install on the System Disk, but instead on another partition, say, the D drive, then rather than changing the default location every time, you can edit the registry as follows:
Before you begin, create a system restore point first.
Now open Regedit and navigate to the following key:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion
Now in the right pane look for the value ProgramFilesDir and/or ProgramFilesDir (x86) depending on whether your Windows is 32-bit or 64-bit.
Double-click on it and in the box which opens up change its Value data from C:\Program Files to say, D:\Program Files.
Click Ok. Exit.
The default directory for the installation of all your programs shall now be D:\Program Files.
If you are using Windows 64-bit, you have to change the value of ProgramFilesDir and ProgramFilesDir (x86).
Go here to learn how to change the default location of the Documents folder or profile personal files or change the default install location of Windows Store Apps.
