What is a system.ini file?
Answer: The system.ini and win.ini files are two files required by Microsoft Windows. They store configuration information for Windows system settings. Other applications may also use their own .ini files to store settings and preferences. However, most .ini files have been replaced by the Windows registry in recent versions of Windows. The registry can be written to by most applications to store user settings and preferences.
Microsoft has a helpful article on replacing the system.ini file if it becomes corrupted or unreadable.