checklist
- first run XAMPP installer by UAC(User Account Control) and Antivirus off and run it as admin
- uninstall previous XAMP installation
- turn off IIS temporarily (which will use default port 80)
- change the port to some free valid port by following below guide
- summary (Locate the file httpd.conf. This file should be found in C:\xampp\apache\conf folder or via config button in XAMPP control panel and search for 80 port and change it to something like 1234
http://complete-concrete-concise.com/web-tools/how-to-change-the-apache-port-in-xampp