It's the same as any other Windows 8.1 install, at least in this regard. If you install a Windows Application, not an App from the Windows Store, then you typically get to choose the location you want it installed to. Most programs default to C:\Program Files, but could be installed on a USB drive, or micro SD card if you'd prefer. Apps from the Windows store however, have a built in default location, C:\Program Files\WindowsApps That folder is owned by TrustedInstaller, and you must take ownership of the folder as an admin if you want to see inside of it. There might be a way to tell it to put things in different locations, but I didn't see an obvious or easy way to do it. It would probably involve editing the registry. If that's not something you are keen on doing, then I advise installing most of your programs as regular applications instead of Windows Store Apps.
