You are missing or having a corrupted important file that is usually part of the Direct X End User Runtime, dinput8.dll
At first, download and install the latest version of the Direct X End User Runtime again, then restart your computer and try again: http://www.microsoft.com/en-IE/download/details.aspx?id=35
Should the error message still show up after a restart of your computer, open Windows Explorer and navigate to C:\Windows\System32. Take a look for a file called dinput8.dll and if present, open an elevated command prompt and type in (confirm both lines with Enter):
regsvr32 /u dinput8.dll
regsvr32 dinput8.dll
This should register the dinput8.dll file in your Windows system, if there was no error, restart your computer and try again.