if your (
Symbian Series 60)phone is slowed down terribaly . and u get system error often , than u need to format and reinstall the OS
all nokia Symbian series 60 phones have a copy of their OS in a built in ROM.
when u format your phone your OS is Restored.
but you back up completly , all files and ring tones SMS and picture messages. u can use use nokia PC suite for this.
then punch in *#7370# it will immidiately prompt you to restart
Select 'yes'
it takes around 5 minutes to complete
make sure u have charged the battery
and once again u have fresh OS
like fresh install of windows