Character structured storage file (Microsoft Agent)
ACS is a file extension for an animated character file used by Microsoft Agent. ACS files contain an animated character that can interact with the user using text-to-speech and speech recognition technologies; may be implemented in both applications and Web pages. ACS files can be used by copying the animated character file into C:\WINDOWS\MSAGENT\CHARS or C:\WINNT\MSAGENT\CHARS, depending on your OS version. ACS files are used by Microsoft Agent, which has been discontinued with the release of Windows 7.
Learn more about .ACS files:
Visit the Microsoft Agent web page.
Learn about Text to Speech at ITKnowledgeExchange.com.