Not even an Administrator knows the passwords or can find the passwords. An Administrator can change his/her own password or the password of any other user and a Standard user can change his/her password, but neither can get the system to reveal the current password. Here's the procedure: http://www.vistax64.com/tutorials/102005-reset-user-account-password.html. Also, an Administrator can access any user's data folders and files directly without logging in as the user (but a standard user can't do this) - though if the files are encrypted, even the Administrator won't be able to read them. If the files are stored on a domain server or domain permissions and group policies are in effect for the servers and the computers in the domain, depending on the setup, even Admininstrators may not be able to do this or what I said an Administrator could do above - it may need to be done at the server level by a Domain Administrator. Even then, I don't believe the Domain Administrator can access the current password, but merely change it.
If you need access to files in another user's account, then ask the administrator to grant you rights to access folders in that account (presumably with permission from that user) - then you don't need the password.
Of course, the easiest way is to ask the user to provide you with his/her password if they are comfortable giving it to you. The fact that you are trying to find a way to get into those accounts without asking them for permission suggests you want to do so without their knowledge - and that isn't right and I will not help you do that.
