Use the Shell_NotifyIcon api function to place your program in the system tray.

Code:
Declare Function Shell_NotifyIcon Lib "shell32" Alias "Shell_NotifyIconA" (ByVal dwMessage As Long, pnid As NOTIFYICONDATA) As Boolean
Public Declare Function SetForegroundWindow Lib "user32" (ByVal hwnd As Long) As Long

Public Const NIM_ADD = &H0
Public Const NIM_MODIFY = &H1
Public Const NIM_DELETE = &H2
Public Const NIF_MESSAGE = &H1
Public Const NIF_ICON = &H2
Public Const NIF_TIP = &H4
Public Const WM_LBUTTONUP = &H202
Public Const WM_RBUTTONUP = &H205
Public Const WM_MOUSEMOVE = &H200


Public Type NOTIFYICONDATA
  cbSize As Long
  hwnd As Long
  uId As Long
  uFlags As Long
  ucallbackMessage As Long
  hIcon As Long
  szTip As String * 64
End Type

Public VBGTray As NOTIFYICONDATA


'Form Declarations:
Private Sub GoSystemTray()
  VBGTray.cbSize = Len(VBGTray)
  VBGTray.hwnd = Me.hwnd
  VBGTray.uId = vbNull
  VBGTray.uFlags = NIF_ICON Or NIF_TIP Or NIF_MESSAGE
  VBGTray.ucallbackMessage = WM_MOUSEMOVE
  VBGTray.hIcon = Me.Icon
  'tool tip text
  VBGTray.szTip = Me.Caption & vbNullChar
  Call Shell_NotifyIcon(NIM_ADD, VBGTray)
  App.TaskVisible = False   'remove application from taskbar
  Me.Hide
End Sub

'Form Code:

Private Sub Form_MouseMove(button As Integer, Shift As Integer, X As Single, Y As Single)
  Static lngMsg As Long
  Static blnFlag As Boolean
  Dim result As Long
lngMsg = X / Screen.TwipsPerPixelX
  If blnFlag = False Then
        blnFlag = True
        Select Case lngMsg
        'right-click
        Case WM_RBUTTONUP
          result = SetForegroundWindow(Me.hwnd)
          PopupMenu MyPopUpMenu
         Case WM_LBUTTONUP
          result = SetForegroundWindow(Me.hwnd)
          PopupMenu MyPopUpMenu
        End Select
        blnFlag = False
 End If
End Sub

Private Sub Form_Resize()
If Me.WindowState = 1 Then
Call GoSystemTray
End If
End Sub

Private Sub Form_Unload(Cancel As Integer)
  VBGTray.cbSize = Len(VBGTray)
  VBGTray.hwnd = Me.hwnd
  VBGTray.uId = vbNull
  Call Shell_NotifyIcon(NIM_DELETE, VBGTray)
  Unload Me
  Set Form1 = Nothing
  End
End Sub