Email Error: Could not instantiate mail function on XAMPP

I encounter two problems that I cannot figure out how to deal with. Firstly, I am trying
to set up a test customer named Mr. Jacques Pires. Having entered his details and hit the 'Submit'
button, instead of seeing the confirmation screen, I receive an error message saying:
'Email Error: Could not instantiate mail function.
Please check Admin->Configuration->Email Options->Email Transport.' I hit the back button
to return to the signing up page and can log in without any problem. Which means his details are entered
into the database. I don't get this.

Secondly, in the XAMPP Control Panel if Mercury is started, I cannot go to the store home page
(http://www.example.com/store or example.com). All I see is a blank page so I have to stop Mercury to get these pages work.
I would be pleased if someone gave me some advice on how to remedy this problem.

The reason you are seeing that error is probably because your Mercury mail server wasn't running or the email transport field in your email options screen of your admin is configured wrongly.

From your second error description, it seems like you may have an XAMPP installation that is different from the book's. This usually causes a port conflict when you attempt to start Apache and Mercury Mail together as detailed in this thread. You might also want to try out the solutions found in that thread.

I think I solved the problem. In fact both of the probs mentioned above were related to a port conflict between Mercury and Apache. In Mercury.INI file, I changed 'Server Port' from 80 to 85 thus letting Apache freely use the port 80. It seems now that everthing runs smoothly. I also left email transport mode set as it is (php) which, at beginning, I thought was the cause of the prob.

Do you think changing Mercury.Ini file this way may cause any problem in the future or I did the right thing?

Many thanks for your support. Appreciated.

Thanks for confirming the problem with the port conflict.

There shouldn't be any problems changing MERCURY.INI that way. Only problem in future would be if another program decide to use port 85 as well.