We have noticed that most of the time, if skype is installed, this error is shown. So, it is worth looking into this first before doing further investigation:

1. Go to Skype -> Tools -> Options
2. Under Advanced Tab click Connection and then uncheck Use port 80 and 443 as alternatives for incoming connections.

If this does not fix the problem then we need to investigate why this could be happening:

1. Bring up a command prompt and run netstat -o -n -a | findstr 0.0.80, The process id is shown on the last column
2. Bring up the Task Manager and make sure that the PID is shown (if PID is not shown then right click on the column title and show PID), then sort by PID
3. Find the process that is shown by the process number in step 1