I don't know how you did it, but good work! Your decryption helped us to see that the file was a registry installation file. It was used to place an executable file into our start up, so all the time since the break in this mystery program has been running.
We had a brief look at the program, but it appears to require a valid username and password combination. To find out what the program has been doing, we will need to gain access. Therefore, we have assigned you the task of examining the program and finding a valid username/password combination. Once you have got one, enter it into your mission conclusion and we shall take it from there.