Ominus Flash Method.
The following is the Ominus method for flashing your X10's. Just remember to download the right files and to have a full charge. Also don't swap files with your devices, X10a = X10a files X10i = X10i files.
First you need to make a Ominus account. It is easy and free, you can do it here, just remember to use your real email and stuff you will need it later. After its down just extract it to your desktop.
Here you can find stock and generic firmwares.
Now open Ominus and go to settings and then server settings and enter in your Ominus user name/password and save the settings.
Now power down your device. In the Ominus top left corner select your phone model, Xperia X10. Then select identify besides it. You will now need to plug in your phone in flash mode. By holding the back button and then plugging it in your computer. Ominus will identify your device and then ask you to turn it off and remove battery then insert again for 5 seconds. Don't turn it on after.
-For any reason Ominus was unable to identify your device it is probably because you don not have the x10 drivers installed on your computer. To do so you can just google x10 drivers or install pc companion or seus and run it once. That way the drivers will be installed.
Now click on Flash, which is next to Identify. When you do a window will appear asking for the application software file and customization software file. In the applications box select the phone.zip (small file) on your desktop or where ever you put it. In the customization box select the other file, android_1233...zip (large file). These are the files that were in your firmware zip. These names are based on the generic Rogers 014 firmware, but you get the point. Like the previous step you will have to plug in your phone in flash mode. Holding the back button and plugging in the USB cable.
--ALSO when you are selecting your firmware files just remember to select "all files" in file types, that way you can see and select the firmware files.
After the process is done, it will say successfully in green on the bottom. Now unplug your device from the computer, and take out the battery and wait like 10 seconds. Now reinsert it and boot your phone, initial boot will take a while since it has just been flashed.
You have now flashed your phone.
Now say you previously done this or you rooted your phone with the wrong version you can use this method to get your phone back to its original firmware. In my case I used the first root method and rooted my phone with the x10i method. So to get it back all i did was download the original ROGER Firmware, and did the steps.