You may want to make sure MySQL is running before you start XAMPP.
https://www.google.com/#q=xampp+start+mysql tells me that it's an oft asked question.
Error: MySQL shutdown unexpectedly.
This may be due to a blocked port, missing dependencies,
improper privileges, a crash, or a shutdown by another method.
Press the Logs button to view error logs and check
the Windows Event Viewer for more clues
If you need more help, copy and post this
entire log window on the forums