Hmmm, I've only heard of this issue with SFML 1.6, but you still might try to apply similar fixes (you can find other posts here (https://www.google.ch/search?espv=210&q=Failed+to+open+the+audio+device+site%3Aen.sfml-dev.org)).All the drivers are the latest. OpenAL32.dll I added to project's directory and to Debug directory. But it still doesn't work :(
Try updating your audio card's driver from the manufacturer's website.
Make sure you copy the OpenAL dll next to your executable, that way you ensure the DLL that ships with SFML gets used and not a random on in PATH.