Windows is installed on an NTFS volume, by default, the 'Program Files' folder can only be modified by members of the 'Administrators' user groups. This can be an issue for programs created for Windows 9x. Those operating systems had no file system security, and programs could therefore also store their data in 'Program Files'. Programs that store their data in 'Program Files' will usually not run correctly on Windows NT systems with normal user privileges unless security is lowered for the affected subdirectories. Windows Vista addressed this issue by introducing File and Registry Virtualization. When this virtualization is enabled for a process, Windows saves changes to the 'Program Files' folder to %LocalAppData%\VirtualStore\Program Files (x86). Localization See also WinFS File system Directory (computing) 64-bit computing References microsoft.com, Microsoft does not support changing the location of the Program Files folder by modifying the ProgramFilesDir registry value microsoft.com, Why is the Program Files directory called Program Files instead of just Programs? producthelp.sdl.com, The Windows system folders - General overview. Windows XP in a Nutshell, By David Aaron Karp, Tim O'Reilly, Troy Mott, page 512 superuser.com, How can I find the short path of a Windows directory/file? helpdeskgeek.com, Why Does Windows 7 64-bit Need Two Program Files Folders? quepublishing.com, The Windows XP Layout, By Stu Sjouwerman, Nov 7, 2003 File system directories Microsoft Windows