Download the EXE fix file and run it according to the general instructions given there.
The initial cause of this could be a virus, so if the above fixes the problem then run your AV scans.
Also download and run MalwareBytes freebie as this can often find what AV's miss. Get it from here (green icon on top right of their page):
I now see this is similar to the process as already given (I didn't realise because of the long lines and small print)
Always pop back and let us know the outcome - thanks