There are some places in the site where the currency is hard coded, this is one of them. You can update this by changing what is on line 174 of the index page to be like this:
<h4>€'. (number_format($row_FeaturedRS['ProductPrice'],2)) .'</h4>
Also, you will need to update the other most popular that is on line 210:
<h4>€'. number_format($row_MostPopularRS['ProductPrice'],2) .'</h4>