I have decided to create one thread that will hopefully answer all question relating to the above, if you think I have missed anything then please post or PM me and if I think it is relevant I will add it to the thread.
I will include links to the direct files needed such as Androxyde & Bin4ry's Flashtool, Zdzihu's xRecovery etc.
On to the topic, this first post will cover rooting of android 2.1 only.
Rooting
Rooting in basic terms is unlocking the phones internal memory, this gives access to the internal system files of the phone and gives the user the ability to edit those files, install new files, run root only apps, flash custom ROM's and many other features.
To root a device your are attacking the device with malware known as an Exploit, the exploit such as "Rage Against The Cage" or "psnueter" use script to attack the system security files until root is gained.
The term root comes from the Linux operating system world, where the most privileged user on the system is called root whereas with Windows that privilege is known as Administrator.
A quote from myself on a thread I answered, some of which is still relevant and some of which is not.
JayJ wrote:Mmm, I wouldn't say rooting was risk free as such as you are infact attacking your phone with malware!
Some PC anti-virus software do not like the software used to root so be aware of that.
"Rageagainstthecage" & "Psneuter" are exploits and are compiled code that basically fools the system into root privileges, "rageagainstthecage"has been patched by SE in the last firmware update 2.0.2.A.0.24 but "psnueter" is the new exploit that has been used to gain root again.
Superuser is a application installed on your phone in most cases at the time of rooting, this app gives you control as to what has Superuser permissions and can gain access to the root of your device. It serves as protection for your phone and only you can control what is given SU permissions.
The advantages of rooting your phone are, being able to uninstall default apps like Moxier, Office Suite, Creatouch, Quadrapop etc, enabling JIT v2, root access apps like Barnacle and ShootMe, being able to flash the DoCoMo kernel for DualTouch and the installation of xRecovery with which you can install themes, flash AOSP (Android Open Source Project) Custom ROM's and do Nandroid Back ups.
Rooting can be undone by doing a software repair via SEUS or PC Companion but you are basically re-flashing the software back onto your phone, therefore any hacks or mods done like uninstalling system apps will be back on your phone. Best if you want to root to leave it rooted unless you need to send it in for repair.
The easiest way to root an X10i (or Mini/Mini Pro) is with Androxyde and Bin4ry's Flashtool, currently at version 0.3.0.0 and a very well thought out Tool. Flashtool in it's current standing will only root SE devices with android 2.1 but I will cover that more later.
Rooting your phone comes with risks, do not do this unless you are confident. I do not take responsibility for you doing something wrong, you do this at your own risk and I will not be held responsible for a bricked phone.
Rooting your Android 2.1 X10i
Step 1. Download Flashtool from here
Step 2. Extract the downloaded zipped file, this will create a folder caller "FlashTool".
Step 3. Double click to open and then double click the bottom application, "X10FlashTool" and this will open up the application.
Step 4. On you phone press, Menu> Settings> Applications> Development> Tick "USB Debugging".
Step 5. Connect your X10i to your PC via the USB cable and click "Root" in the top left corner of the X10FlashTool window. The application will run the script and upon reboot your device will be rooted. Superuser will also be installed during this process.
Step 6. Once reboot is completed you can check root by clicking "Ask Root Perms", make sure your screen is active so you can grant Superuser permissions when the pop-up appears on your phones homescreen.
Root access complete.
You now have Read/Write privileges to system files, you can install root needed applications such as "Titanium Back Up" to remove system applications and "Root Explorer" to edit system files such as the default.prop, build.prop and bootanimation zip etc. These applications will require you to Superuser permission to be Allowed once at the start of the application.