To hard reset your Sony Ericsson Xperia X10?
All you need is a SEUS update.
SEUS (Sony Ericsson Update Service) is program which helps you to connect to the main Sony Ericsson Web Site easily and upgrade your phone with the latest software available for it. It can be downloaded from the main SE web page.
Visit this official webpage for sony ericsson handsets support and follow the instructions there.
For soft reset follow the instruction below:
1 From the Xperia 10 Home screen, tap the applications bar.
2 Tap Settings > SD card & phone storage > Factory data reset > Reset phone.
3 Enter your screen unlock pattern.
4 Tap Erase everything.