You cannot use Timer Control in windows service it is because Timer Control is located at System.Windows.Forms.

Instead, use server timers from Timer namespace. To do this,

Friend WithEvents mTimer as New Timer.Timer

Protected Overrides Sub OnStart(ByVal args() As String)
mTimer.Interval = 6000 ’6 seconds

mTimer.Enable = true
End Sub
Private Sub mTimer_Elapsed(ByVal sender As Object, ByVal e As System.Timers.ElapsedEventArgs) Handles mTimer.Elapsed

‘Put your code here to execute
End Sub