Tools Required :
Nemesis Service suite (NSS)
Nokia PC Suite
1. Connect your phone in PC Suite mode
2. Open Nemesis Service suite (NSS)
3. Then click on scan for new devices button (top right hand side)
4. Click on phone info button.
5. Now Click on Scan.
6. Select Permanent Memory.
7. Click on Read.
8. It will read the permanent memory file and save it on the disk at following path.
9. Open the .pm file using Notepad.
10. Now scroll until field , and on the 5th Record (5=) your security code is saved at there.
11. Like 5=31313131310000000000
12. Remove all 3 digit and it will be 31313131310000000000
13. 11111 is your security code.
source: Reset Nokia Security Code - Video