Adobe Illustrator CS5.1 was released in . Adobe ended support for CS5.1 in April 2017 . The software is now considered “end-of-life” (EOL).
To ensure smooth operation of Adobe Illustrator CS5.1, users should: Adobe Illustrator Cs5.1 Amtlib.dll
Are you experiencing a specific when launching Illustrator, or did the file disappear after a system update ? amtlib.dll is missing from your computer - Adobe Community Adobe Illustrator CS5
There are several reasons why Amtlib.dll errors may occur in Adobe Illustrator CS5.1. Here are some possible causes: Adobe Illustrator Cs5.1 Amtlib.dll