[Sony Ericsson XPERIA X10 Mini] ddz334:
Again thanks to xda. Flashed a new 2.3.7 ROM in x10 mini. Here are the steps from scratch.

Check the update, kernel and firmware version before proceeding.

The whole procedure involves

1. Rooting (with Busybox installing)

2. Installing the recovery

3. Unlocking the bootloader (this tutorial is for only unlocked, first hand, SEMC certificate devices)

4. Flashing a new kernel

5. Flashing the ROM and google apps

6.

Before proceeding backup the contacts, messages, notes etc. (Titanium backup can be used after rooting)

I. Rooting

1. Download the Superoneclick from here. http://xdaforums.com/attachment.php?attachmentid=485088&d=1294607042 Unzip the contents into required folder.

2. Enable the option to install from unknown sources in phone

3. Enable usb debugging in the phone

1.

di. It is desirable to have sony ericsson update service installed and the phone recognized (with necessary drivers installed)

5 .run the superoneclick.exe

6. insert the cable and select charging in phone

7. select root

yes it is done. Reboot your phone. Go to the apps menu and confirm a app called super user is installed.

Then go to the market and install following 3 apps

1. busybox

2. root explorer (for later use)

3. astro file manager (if needed)

II. Installing the Recovery

1. Download the necessary files from here. http://xdaforums.com/attachment.php?attachmentid=616283&stc=1&d=1307259517

2. Unzip the files and copy the bin and xbin folders in system folder to sdcard of phone

3. Open the root explorer and mount as r/w instead of r/o

4. Then move the contents of bin folder to /system/ bin folder in phone and xbin to xbin (only contents, not folder)

5. Change permission of all the files, by ticking all the boxes.

That is it. You have now clock work mod recovery. This can be confirmed by using astrofile manager to see if there is respective files moved. Or power off the phone and switch it on again, when the logo of sony ericsson comes keep pressing and releasing the back switch of phone. If everything have gone correctly till now you will enter the recovery mode.

III. Unlocking the bootloader (for installing a custom kernel)

1. download the flashtool from (0.5.3 -I used) here. http://androxyde.github.com/Flashtool/

2. before advancing further download the required ROM (for me miniCM7 from http://minicm.googlecode.com/files/MiniCM7-2.1.6.zip )and google apps from http://cmw.22aaf3.com/gapps/gapps-gb-20110613-signed.zip and copy both to the root of sdcard

3. open the install location of flashtool and install the ggsetup-2.2.0.11.exe file inside and install Gordon's Gate found in /drivers folder

4. then restart the computer, open the task manager and kill any process named adb.exe

5. donot open flashtool after this till needed.

6. Download the s1tool to confirm the unlock certificate of phone from http://db.tt/OrOQO33 and unlocking tools from here http://db.tt/0zUMR5S4

7. Unzip the s1 tool to the designated folder and run the s1.exe. Switch off the phone. Select the Do Job button and wait.

8. Connect the phone in flash mode (switched off and back button pressed)

9. proceed further only if the screen shows semc simlock certificate

10. unplug the phone, switch it phone, connect to the computer

11. run msm7227_semc.cmd in the directory you unzipped the unlocking files to and press any key to start the unlocking process.

12. If everything goes correctly the log will show press any key at the end.

Now you have unlocked the bootloader we can proceed to kernel flashing

IV. Flashing the kernel and ROM

1. download the require kernel.ftf from auther's site (for me the kernel suiting my ROM was nAa kernal from http://minicm.googlecode.com/files/E10_nAa-08_2.6.29.6-nAa-08.ftf

2. copy this to the /firmware folder in flashtool install folder

3. run the flashtool and select flash, then flashmode

4. select the desired kernel

5. switch off the phone and connect in flash mode when pop up requests

6. disconnect phone when the tool says so

7. switch on the phone and enter the recovery mode when kernel logo comes by repeatedly pressing and releasing the back switch

8. in the recovery mode, do a backup from backup and restore option (up and down by volume keys and select by middle switch)

9. do a factory wipe data

10. then flash the ROM zip by selecting the option install zip from sdcard option followed by gapps zip flashing

11. finish this and take reboot (long)

Enjoy the new experience.