After the excitement of installing a new custom ROM, you might want to roll back to the original one that came pre-installed on your device. Reasons for this might be that you just don’t get on with any custom ROMs , or perhaps you want to sell the device as it was when it was new.
Most devices when rooted allow for installation of ClockworkMod recovery, or another custom recovery. When rooting your device for the first time, its strongly advised to make a backup of your current ROM, just in case of any problems or if there is data on there you may need later. Using ClockworkMod makes backing up and restoring ROMS an absolute breeze, and this guide will take you through using ClockworkMod and restoring.
But what if you forgot to run a backup before installing a custom ROM? Luckily there are other solutions available in getting your phone back to its original state. The easiest of these involves downloading a RUU (Rom Update Utility) from the manufactures website for your device, but these are not always available so we will show you an alternative.
Restoring from Backup
An easy way to go back to stock ROM is by restoring from the backup you made when you first rooted. If you didn’t do this , then skip to step  . Boot into recovery either from within your ROM , or by holding down the volume when you boot the phone.
Wipe Old Rom
Before installing any new ROMs its very important to totally wipe everything on the device, except the SDcard. This is done from within ClockworkMod by clicking ‘Factory Restore’ and also from within Advanced ‘Wipe Dalvik Cache
Restore Stock ROM
Once you are in recovery navigate to ‘Backup and Restore’ and then ‘Restore’. You should then see a list of your backups by date. Choose the one that corresponds to your standard ROM and then click on it. The device will then be restored to exactly the same state as when you made the backup
Find Stock ROMs
Ok, so what if you didn’t make a backup of your stock ROM? Luckily there are stock ROMs available online to flash in the same way as you would a custom one. First off, navigate to XDA and choose your device from the list http://forum.xda-developers.com/index.php
Once you have found your device enter the relevant ‘Android Development’ section. Quite often stock ROMs are stickied to the top, or from within a ‘newbies’ guide, if not , then do a search. You are likely to have a choice of rooted or unrooted stock ROMS.
Once you have chosen your ROM, copy it to your Sdcard by mounting the SD on your computer and dragging the zip across. Unmount the card and then reboot into recovery mode. Then make sure to do a factory reset and wipe Dalvik.
Install Stock ROM
Next up, just choose ‘install zip from Sdcard’ and then ‘Choose zip from Sdcard’ and then choose the zip file from the card. Click on it, then choose yet. The ROM will then install in the same way as a custom ROM.
Back to Square One
Once the ROM has installed, reboot and you should see the device as it was when you got it. If you chose a non-rooted ROM, then obviously you will have lost root permissions , and will need to re-root if you want it back.
Installing from RUU
If there is no stock ROM available for your device , you can also try getting a RUU for it direct from the manufacturers website, or elsewhere on the web. This is a executable file you run on your computer rather than on the phone to install a ROM.
Nearly all RUUs are not rooted and some may not support a custom bootloader if you installed one on your phone. Each manufacturers update process is different, but most involve double clicking the RUU with the phone plugged in and following the instructions.