Stuff you need to backup are Contacts, Messages and GDFS. You can backup Contacts and Messages with MyPhoneExplorer. Backup GDFS with XS++ 3.1

Useful:
XS++ 3.1 Guide-Flashing,Customizing,Recovering - Top Sony Forums
Download MyPhoneExplorer 1.6.7 - With this program you can administer its Sony-Ericsson mobile phone simply - Softpedia