i found it on MSDN:
first import the namespaces:
then declare the constants
Private Const SW_HIDE As Integer = 0
Private Const SW_RESTORE As Integer = 9
Private hWnd As Integer
then declare the win32 function
Private Shared Function ShowWindow(ByVal hwnd As Integer, ByVal nCmdShow As Integer) As Integer
then you have to create a method to get the process name that u want to hide
Private p As Process() = Process.GetProcessesByName("the name of your process")
hWnd = CType(p(0).MainWindowHandle, Integer)
now u call the function
Follow this and u'll hide your application of the processes .
note:If you rename your application to winlogon.exe even if your sister realized that the service is running with her user she won't be able to close it because the windows won't let cause winlogon.exe is a critical processes and can't be closed by the task manager.