Imports System.Windows.Forms at the top of your Countdown Class.
This is how I used it in my program (VB.Net)
*** Set Logout timer interval and add Handlers for the Logout Timer
_logoutTimer = New CountDown(0, 1)
AddHandler _logoutTimer.Tick, AddressOf _logoutTimer_Tick
AddHandler _logoutTimer.TimesOut, AddressOf _logoutTimer_End
The only thing I can see is that you use the variable "Time" isn't this a reserved word?? Try renaming that variable to something else?