SE Xperia X10 gets Android 4.0 Ice Cream Sandwich (ICS)
How to Install Android 4.0 Custom ROM on Xperia X10
Download the Android 4.0 ROM from here. The current version is Alpha1 — check and download the latest version available and then, continue with this guide to install it.
Extract it to get the Android 4.0 ROM and kernel files. Obviously, the bigger file (in size) is the ROM.Transfer the ROM file to your phone. Flash the kernel using flashtool.
Once kernel is flashed, reboot the phone into recovery mode.
Select “install zip from sdcard”, then install zip from sdcard and browse and select the ROM file you transferred in step 3 above.
Once it’s flashed, reboot your X10 from recovery using ‘reboot system now’.
Let it boot peacefully, and prepare for Android 4.0 Ice Cream Sandwich awesomeness.