The migration of Windows XP to Windows 8.x is the same possesses and the same problems as like you can meet during the migration of Windows XP to Windows 7.
For the migration of the user data, we make things for the hand and/or with USMT., Just dont forget to use the last version USMT
Step-by-Step: Basic Windows Migration using USMT for IT Professionals
Dont forget: You cannot use USMT 6.3 to migrate settings from Windows XP to Windows 8.1 (Workaround: Run backup with USMT 5.0, restore with USMT 6.3)