DLL-Files.com Support says:
During the last month we have received an astounding number of requests for this x39ish.dll . As far as I can tell, people want this file for downloading and playing illegally pirated games. Currently, there seems to be a misconception that with this file, one can play GTA V on PC (not even released yet!).
With this in mind, check out this article on how thousands of people have been tricked into happily installing Viruses and spyware: http://goo.gl/cGnFME
Surf safe, and do not pirate! DLL-Files Support