I already have MySQL installed on my PC ... Also, I have Apache installed. By downloading XAMPP, will this overwrite my current MySQL and Apache that I have installed on my PC. Also, I have IIS installed ... I have been told that Apache can co-exist with IIS. Any help will be appreciated. Thanks.
It will not overwrite your current MySQL and Apache; however, you can only have one Apache and MySQL process running, unless you use VirtualHosts; search this forum for more info on that.
Not sure about IIS, I don't use IIS. Just search it on Google.