You can find the USB insertion and removal using WIN32 API as well as WMI. This post is about detecting USB insert and removal using WIN32 API.

    Private WM_DEVICECHANGE As Integer = &H219

    Public Enum WM_DEVICECHANGE_WPPARAMS As Integer
        DBT_CONFIGCHANGECANCELED = &H19
        DBT_CONFIGCHANGED = &H18
        DBT_CUSTOMEVENT = &H8006
        DBT_DEVICEARRIVAL = &H8000
        DBT_DEVICEQUERYREMOVE = &H8001
        DBT_DEVICEQUERYREMOVEFAILED = &H8002
        DBT_DEVICEREMOVECOMPLETE = &H8004
        DBT_DEVICEREMOVEPENDING = &H8003
        DBT_DEVICETYPESPECIFIC = &H8005
        DBT_DEVNODES_CHANGED = &H7
        DBT_QUERYCHANGECONFIG = &H17
        DBT_USERDEFINED = &HFFFF
    End Enum

    Protected Overrides Sub WndProc(ByRef m As System.Windows.Forms.Message)
        If m.Msg = WM_DEVICECHANGE Then
            Select Case m.WParam
                Case WM_DEVICECHANGE_WPPARAMS.DBT_DEVICEARRIVAL
                    lblMessage.Text = "USB Inserted"
                Case WM_DEVICECHANGE_WPPARAMS.DBT_DEVICEREMOVECOMPLETE
                    lblMessage.Text = "USB Removed"
            End Select
        End If
        MyBase.WndProc(m)
    End Sub

The WndProc() helps to detect Windows Messages from OS. When a USB inserted or removed, Windows OS will send some message (WM_DEVICECHANGE) to all the applications. And the WParam property of that message will contains the details of the device event. The system broadcasts the DBT_DEVICEARRIVAL device event when a device or piece of media has been inserted and becomes available. The system broadcasts the DBT_DEVICEREMOVECOMPLETE device event when a device or piece of media has been physically removed.

Happy Programming