There are several reasons that may cause you to reset your Sony Ericsson W300i phone. Ultimately, if your phone is not performing at its full potential, or if you notice a lag or are unable to access applications, you may need to reset the device back to its factory settings to remedy the problem. Resetting your phone will delete all of the information off your device and should be the last troubleshooting step.
Power on your W300i phone and locate the "Settings" menu.
Select "General" followed by "Master Reset."
Select the option "Reset Settings" to restore the settings on your device or "Reset All" to delete all the content from your phone.
Select "Continue" and confirm your decision to reset your phone. Wait for your device to restart.
Backup any important files onto a memory card or PC before you reset W300i phone.