Nokia site eken OS eka update karanna puluwan.
If u just want to reinstall the current virsion, u can format the phoe by Switching on the phone while pressing
-green dial key
-the star key(*)
-the number 3 key
Remember to have battry full.
do not let go of the keys until you see a formatting screen.
Then u ll have a fresh OS (every thing in the phone memory will be gone)