How to recover Windows serial number?

Question

Windows

Hello! The other day the hard drive "died", I had to reinstall the system. Windows 7 HP, purchased honestly in the summer of 2012.
Problem: the serial number is not recorded anywhere, the letter has not been preserved. In my head - 20 characters (4 groups) out of 25, I don’t remember only the 3rd group, that is A1BCD-23456-?????-EFG7H-IJK89:.
A possible solution is to contact Microsoft, file a recovery application, wait 7 days, then something else, and so on... but maybe there is another way?
Question: are serial numbers a set of random letters and numbers, or is there some kind of logic in it and it is possible to restore at least some numbers from the lost ones?
Update: The problem was solved in a natural way: I remembered the missing characters. Y6F2W:)
Thank you all for your support!

Answer 1

THERE ARE 20 SYMBOLS IN THE HEAD..... O_O that's what life-giving Windows does to people