I'm not sure what's the scope of your question, but I'll begin with the basics.
Here's is where you do Active Directory stuff. It's in C#, but you can convert it to VB.net.
http://www.codeproject.com/KB/system/everythingInAD.aspxSom
e information on using ADO.NET:
http://www.vbdotnetheaven.com/Articles/ArticleListing.aspx?SectionID=2&SubSectionID=96
http://www.functionx.com/adonet/index.htm
http://vb.net-informations.com/ado.net/vb.net-ado.net-tutorial.htm
Let me know if you have other questions.
Arun