Here's the instruction on how to format or reset the Nokia C5-03 to factory fresh default settings.
Note: This may only advisable if the phone experiencing frozen or hang problems, burned out by excessive use or installing 3rd party applications. You may need to back up all important data stored on the phone before you proceed, this process will delete the files you installed on Nokia C5-03.
Nokia C5-03 Soft Reset:
This will not harmed your data . Soft reset only restores .ini files from Flash ROM on board memory of your Nokia C5-03.
1.). Dial *#7780#
2). Press Ok/Yes
Nokia C5-03 Hard Reset
This will delete your data and installed applications. Hard reset will restore your Nokia C5-03 to default factory setting.
1). Turn off Nokia C5-03
2). Take out the battery and reinsert it, turn it on
3). Dial *#7370#
4). Press Ok/Yes
Nokia C5-03 Hard Reset through button combination.
1). Turn Off the Nokia device
2). Pull out the battery and reinsert it back again, then Power it ON
3). Simultaneously press and hold *+3+Call Button (green/ok button)