Password protecting a program

I have a couple of MFC programs I'd like to password protect to keep unauthorized users from executing. I have created a password dialog which allows
the entry of a user name and password. What I have done is hardcoded a password in for now, what I'd like to do is have a little more flexibility
in adding users, changing passwords ect. I don't want to reinvent the wheel by coming up with my own scheme to do this since 95/98/NT already
have this functionality. Are there api's I can use to do this? At the least I could create an old style .pwl file, but I want to encrypt the password, is there
an API I can use for this?
Thanks for any advice,

Dan