single sign-on with client/server applications

Hello List,
Anybody got experience with this type of situation using Active Directory and VB? The requirement is for passwords to change periodically, an alternative is to expire the Oracle password but I was wondering if people are going to Oracle Internet Directory and synchronizing and are happy with the setup.  

Scenario 1
User logs into his PC via Active Directory. User chooses to start application X. Application X asks him to choose a database. Application X connects to chosen database. User does not need to provide his credentials again. Later on, user repeats the same procedure on application Y. Scenario 2
Continuing on from scenario 1, user chooses to start application Z. Application Z asks him to choose a database as well as giving him the option to connect using a different userid than his own. If user chooses a different userid, then he must provide a password.

Questions
1) Is possible to fulfill the above scenarios? 2) If so, can you tell us what additional software (from Oracle Corp. or otherwise) that we would need?
3) Can we have Active Directory be the "authenticating" server?

Operating environment
1) Oracle 8.1.6, 8.1.7.4, or 9.2 Enterprise Edition RDBMS hosted on AIX (4.3 or 5.1) servers.
2) Currently, using database authentication (accounts and roles created in each database).
3) Applications are home-grown client/server apps written in Visual Basic (VB6 and VB.NET).
4) Usually, each application connects to one and only one database. 5) The user determines which database to connect to during the login process.

6) The applications run on Windows 2000 client PCs.
7) Microsoft Active Directory used to login to the PCs.
8) Not running Oracle Application Server.
9) Not licensed for the Advanced Security Option.

TIA   Bruce McCartney
bruce.mccartney_at_dbinfosystems.com
<BLOCKED::mailto:bruce.mccartney_at_dbinfosystems.com>    

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