My cell model is Nokia 7610 supernova. It was working properly. I switched it off since the charge was low. But when i switched on again, the display is not working from then.

Hi what kind of lock code are you asking for? Is it a phone lock or a network lock?
If it is a phone lock, You must do a master reset for your Nokia 7610. This could restore your phone with default factory settings.
If it is a network lock, You need to enter the unlock code. You can get the unlock code either from your network provider or from any trusted vendor online. For example you can get the unlock code from www.unlocking4u.com/nokia-7610-supernova/rs6wp9/ at affordable cost.
Here are the steps for unlocking a Nokia 7610 SUPERNOVA,
1 - Switch on your Nokia 7610 SUPERNOVA without any sim card.
2 - Don't bother as to what is displayed on your Nokia 7610 SUPERNOVA.
3 - Compose #pw+CODE+1#.
4 - The Nokia 7610 SUPERNOVA would then display the message "SIM Restriction Off" and will be unlocked!

you can contact the mobile service provider......

12345 is the default code for all nokia.Good luck

if you Forget your Nokia 7610 supernova security code , so nothing to worry, i am giving you its Master Code , it will solve your problem...
Security Master code: 3544116331

PLS NEW CAMERA SOFTEWEARE INSTALASION

try to reformat FIRMWARE of your celphone

Please try again with code 12345. If fail get it unlocked at www.unlock-zone.com

at first you will check your msg centere number if it is correct then you will contact with your service provider

Step 1 : Power the phone off Step 2 : Press down talk/green + 3 + * Step 3 : ...
*#7780# ask to put security code i put 00000/12345 but not yet

Try this friend,
http://www.getjar.com/mobile/6865/nimbuzz-for-nokia-7610-supernova/