Windows Thin PC is the successor to Windows Fundamentals for Legacy PC's. It is based on the embedded version of Windows 7 (Windows Embedded Standard 7), and serves as a thin client which can be used on older computers for users who do not want or do not have the option to upgrade hardware. The operating system is not available in the retail market, so the only legal way to obtain Windows Thin PC is through Microsoft's Software Assurance program, which is targeted at enterprise markets. Windows Thin PC uses KMS/Volume license activation.