Encryption method

I’m sure what I want to know only borders on the legal … just. If so, do tell me and I’ll go away!!!

We are producing an add-on to an existing software package that uses SQL Server. This package holds the logon password for the system in an encrypted form as a simple, text ini file. I have some examples of these text strings with their actual, real password equivalents. Do you know of a way or some software that I can purchase to discover the encryption method employed so I don’t have to ask users to retype a password?

Regards.