andrisi wrote:What if I already have MySQL installed? Will XAMPP us it
No
andrisi wrote:...or will it install another one, or...?
Yes - the lastest version of XAMPP usually includes the latest version of MySQL.
andrisi wrote:What is the "standard procedure" for this case? Thanks.
Don't try and run both instances of MySQL at the same time as this is not possible.
Run
xampp\xampp-portcheck.exe before running the XAMPP instance of MySQL to see if your previous version is occupying port 3306. If it is then the XAMPP instance of MySQL will not start.