[Xampp] Añadir servicio MySQL a una instalación existente

Here is how I did it:

1. Re-run the installer and install with MySQL into a different folder. (These instructions assume c:\xampp2)
2. After the installation finishes, move the mysql directory from the new install into the old install. (I moved c:\xampp2\mysql to c:\xampp\mysql) You can then delete the second installation folder.
3. Be sure xampp is not running and edit c:\xampp\xampp-control.ini, looking for the [EnableModules] section. Set MySQL=1.
4. Restart xampp. The MySQL buttons should be enabled. Click the Config button next to MySQL and edit the my.ini file. Do a search and replace, changing all instances of xampp2 to xampp.

Now you can hit start, and MySQL should start up. Note these instructions assume c:\xampp is your desired install location, adjust accordingly.