http://localhost:80 is not working on running Apache server through UniServer ZeroXIII

I am unable to configure a PHP/MySQL/Apache environment on my local machine using UniServer ZeroXIII.

In my Uniserver ZeroXIII control panel the Apache and MySQL status is shown as started, but localhost URL is not working.

When I start Apache in the Uniserver, I get the following error message Failed to execute "http:\localhost:80\index.php" :87

I have tried the following methods but still I am unable to fix this issue:

  1. I tried to reinstall after uninstalling several time.
  2. I tried to restart Uniserver several time
  3. I changed the "Listen 80" to Listen localhost: 80, localhost: 8080, 127.0.0.1:80, 127.0.0.1:8080, but it still does not work.
  4. I changed the port apache= 8080 and apache ssl port = 444.

I remember that, everything worked very well when I first tried. And when I try again it has error. I am using Windows 8.1 and Avast Free antivirus. Installed Uniserver in directory C:\\Uniserver location, and my program files and OS are in the same directory in C:.