Forgot security code - Nokia 7310 Cellular Phone

First install all the necessary drivers for your phone.
Then you'll need Nemesis Service Suite to read the flash memory (find it at Phone Info -> Permanent Memory tab ->Read in Nemesis Service Suite a.k.a NSS, not on the phone). After the entire permanent memory is dumped, you should find a file in C:\Program Files\NSS\Backup\pm or C:\Program Files (x86)\NSS\Backup\pm.
The file name should be your imei.pm
For example(358123123123123.pm). Open it with a good text editor (Notepad++ recommended), search for a line (CTRL+F) that contains the following string:
[308]
Then there should be another two lines beneath it that look like this:

0=00 or other numbers
1=31323334350000000 <--this is the line you need
In this example, the security code should be 12345 because you take only the even positions until you have 5 digits then you ignore the rest of the line.
3 1 3 2 3 3 3 4 3 5 0 0 0 0