Your installation program should copy all necessary executable and data files to the appropriate directories. It should never copy these files to the WINDOWS or SYSTEM directories. Instead, it should create a directory in the Program Files directory and copy its files there. If the Program Files directory does not exist on the root of the hard disk, your installation program should create it.
It is recommended that your installation program use a long filename for the directory, such as the application name or another descriptive and unique name. Your program should copy the main executable file for your application and any other executable or data files that the user may want to open directly to the newly created directory. For example, if your application's name is "My Wizzy Application.Exe", your installation program should create the \Program Files\My Wizzy Application directory, and copy My Wizzy Application.Exe to that directory.
If you have any other executable or data files, such as .DLL and .HLP files that are specific to your application, your installation program should create a subdirectory, named System, in your application's directory. It should copy the remaining files (except shared files) to this new directory. For example, if your application has a DLL named MWASUP.DLL, your installation program should create the \Program Files\My Wizzy Application\System directory and copy the DLL there.
If any of your executable or data files are shared, your installation program needs to copy the files to yet another directory, depending on how widely the file is to be shared. A file is system-wide shared if many applications from different vendors use it. For example, the VBRUN300.DLL file is a system-wide shared file, because it is used by any application built with Visual Basic. A file is a shared file if it is shared by a set of applications from the same vendor. A common example of this would be an office suite that might use the same drawing program for its word processor as it does for its spreadsheet.
Your installation program should copy all system-wide shared files to the Windows SYSTEM directory. If a given file already exists in this directory, the program should overwrite it with your application file only if your file is a more recent version. The GetFileTime, GetFileVersionInfo, and GetFileInformationByHandle functions can be used to determine which file is more recent. After copying a DLL file, if your installation program does not use Microsoft Installer Technology, it should increment the usage counter for the DLL in the registry. For more information about the usage counter, see Adding Entries to the Registry. Microsoft installer technology has a configuration database that keeps track of all of the components and files needed for all applications that use Microsoft installer technology on a particular computer. This makes it easy to manage shared components.
Your installation program should copy all shared files to a System directory in the \Program Files\Common Files directory. If the directory does not exist, the installation program should create it. Again, it is recommended that your program use a descriptive and unique name. For example, if there is a shared file named My Wizzy Speller.Exe, your program should create a directory named \Program Files\Common Files\System and copy the file there. The location of the Program Files and Common Files directories is registered (using the macro REGSTR_PATH_SETUP) in the HKEY_LOCAL_MACHINE root under the SOFTWARE\Microsoft\Windows\CurrentVersion key. The value names are ProgramFilesDir and CommonFilesDir.
When your installation program installs applications on computers running Microsoft® Win32s® with Windows version 3.x, it needs to be aware that the system does not support long filenames. Your installation program will need to use the short 8.3 filename equivalent for Program Files and Common Files, which is Progra~1 and Common~1, respectively.