Xperia:Installing a ROM

A ROM, in this context, is the firmware created or adapted to be used on your phone.

Stock ROM Installation Instructions

Installing a stock ROM is basically going back to a firmware officially released by Sony Ericcson. It's usually a good way to recover in case you mess something up while flashing custom stuff. Note that many apps will no longer work in a stock setup, as this phone is quite old in Android years. Also note that this will undo custom ROMs, recoveries, and root methods.

You will need Xperia:FlashTool for this process.

1. Turn off the phone and connect a USB cable to the computer.
2. Hold down the search (magnifying lens) button on the phone and connect the USB cable to it. The light on the power button should be blue.
3. Copy your firmware *.FTF file into the firmwares folder where FlashTool is installed.
4. Open FlashTool and wait for it to detect the device.
5. Click the lightning bolt icon, make sure "flash mode" is selected, and click OK.
6. Select your firmware from the list and click OK.
7. FlashTool will prompt you to unplug the phone, make sure it is off, then hold down the back button and reconnect the USB cable.
8. When FlashTool is done, disconnect the phone and power it on.

Custom ROM Installation Instructions

Custom ROMs are preferred by many for Android phones, especially on older models. They often have undesired apps and features removed (or not included to begin with), support a wider variety of devices, and include tweaks and modifications that boost the device's performance and longevity. Many are built on newer versions of Android that are officially unsupported for the phone, but work well regardless. Some ROMs may have specific installation instructions; if so, they'll be detailed in the ROMs list. Otherwise, you can follow these general instructions.

1. If you are starting from stock (which is sometimes a good idea), make sure you have USB debugging enabled.
2. If you haven't yet done so, install a custom kernel, or at least a custom recovery. Which kernel to use may be determined by the ROM you're going to install.
3. Copy the ROM's zip file and any of its extra files to the phone.
4. Boot the phone into the custom recovery.
5. Find the wipe/format options.
6. Wipe System, Data, cache, and Dalvik cache. Do NOT wipe anything else.
7. Go back to the recovery's install option. Locate the ROM's zip file and install it.
8. If the ROM comes with a GApps (system apps necessary for running Google services) package, install that as well.
9. At this point, you should be able to reboot into the OS. It will take several minutes for the initial setup. If you have any other extras for the ROM, such as AdrenoBooster, you can go back into the custom recovery to install them.

Warning

Some custom ROMs are for specific models of Play; however, some ROMs specified for the R800i may still work on the R800x, but with the loss of properly working cell radios. There are many, many more custom ROMs out there, most of which can be found on XDA-Developers.

It is highly recommended that you thoroughly read the first post in a ROM's support thread before trying to install it. Many of these have specific requirements or issues to be aware of.