Before you flash a rom to your phone or make any changes, please make a nandroid backup. You should not even think about flashing another rom until a backup has been made. Its easy to do and will save you lots of headaches down the road. 1. Boot into the clockworkmod recovery console. 2. Select Nandroid. 3. Select Backup. Wait for it to finish. 4. Proceed with what you had planned.