I have been using XAMPP for a while now, but this morning seems like something kinda went wrong.
I am using XP with XAMPP 5.3.5.
I develop at home, and I use my other computer as a server. running PHP/APACHE/MYSQL on XAMPP.
I am using phpMyAdmin to manage my db.
I noticed that my webpage was not responding too quickly, would lag and return an error about not being able to connect to the DB. (I lost that error message, I tried too many times).
Rule #1: DO NOT USE root for application programming.
Try logging onto the database using the mysql client and your root password. If that doesn't work, you may have to reset your root password. The MySql docs have instructions for that.