its f9........normally nokia s40 are unaffected by virus since they only support java platforms software.........since ur bearer u may use.. following steps..
1 Switch Off the device.
2 Press and Hold down the keys Green/Talk + 3 + *.(hard Format)
3 Switch On the device.
4 If everything goes well then you will see "Formatting" screen.
but dont leave the buttons until u seen the formatting screen or else ur mobile started.......it will crashes ur mobile sofware......
or else
dial *#7370# ? not sure if it resets S40 models, but nothing happen if u try it.
Or you can try to do a firmware update (
http://www.nokia.com/softwareupdate ) as that'll reset it, too.
If neither helps, any Nokia authorized repair center should be able to help.