Google Chrome on Windows encrypts your saved passwords using the Windows encryption function CryptProtectData. In order to decrypt the saved password not only do you have to be logged in with the same user password Chrome used to save it, but also be on the same computer.
From your description I understand you only reinstalled Windows, but are on the same computer. Try changing your password or create a new account with the same username and password you used before reinstalling to decrypt the passwords with ChromePass.