You can download and install the ac1st15.dll if you are facing errors such as:
The program can't start because ac1st15.dll is missing from your computer. Try reinstalling the program to fix this problem.
There was a problem starting ac1st15.dll. The specified module could not be found
Error loading ac1st15.dll. The specified module could not be found.
ac1st15.dll is either not designed to run on Windows or it contains an error.
ac1st15.dll is not designed to run on this version of Windows.
How to Install
Download and copy over ac1st15.dll to the C:/Windows/, C:/Windows/System32,C:/Windows/System/, and C:/Windows/SysWOW64 directories.
Also copy it to the directory where your program is installed. If the program still shows the error, you might have to search on Google on where to copy over the ac1st15.dll file.