ADSI is Active Directory Services Interface. It's a product by Microsoft and works in conjunction with VB. You can Download ADSI from Microsoft. It allows you to access and modifiy NT related components without bulky coding.

Example: ( This Enumerations Computers from a Domain)
'-- Declarations
Dim Domain As IADsContainer
Dim comp As IADsComputer
Dim vfilter As Variant


'-- Initialize
Set Domain = GetObject("WinNT://" & sDomainName)
vfilter = Array("computer")
Domain.Filter = vfilter

'--
' Error Trapping
On Error GoTo errhandler
'--
'--Information Settings
FrmMain.StatusBar1.Panels.Item(1).Text = "Enumerating Computers, Please Wait"
FrmMain.StatusBar1.Refresh

Dim nodX As Node
Dim x
Dim i As Long, j As Long, k As Long
With FrmMain.TreeView1
With .Nodes
For Each comp In Domain
Set nodX = .Add(sDomainName & Computers",tvwChild,sDomainName & comp.Name, comp.Name, 22, 22)

Next comp
End With
End With

'--
' Resets the Variables Used by the Application
FrmMain.TreeView1.SelectedItem.Expanded = True
FrmMain.StatusBar1.Panels.Item(1).Text = ""
FrmMain.StatusBar1.Refresh
FrmMain.MousePointer = vbDefault

Exit Sub

errhandler:
FrmMain.StatusBar1.Panels.Item(1).Text = "A Error has occured, Please Check Settings"
FrmMain.StatusBar1.Refresh
FrmMain.MousePointer = vbDefault