killing a process from windows service

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VB

.NET

.NET4

service

I am trying to keep the explorer.exe KILLED till an event.

I mean i have an xml file which i read from my windows service background worker. It waits for a value, till than the explorer.exe should not execute, its for security purpose.

I have tried till now :

While (True)
                Dim doc As New XmlDocument
                doc.Load("C:\Users\Alpha-Guy\AppData\Local\Packages\new-design_sa0tb4645bqbp\LocalState\metadata.xml")
                Dim list = doc.GetElementsByTagName("authenticated")
                var_auth = list(0).InnerText

                If var_auth = "0" Then
                    Dim pro As Process
                    pro = Process.GetProcessesByName("explorer")(0)
                    If pro IsNot Nothing Then
                        pro.Kill()
                    End If
                End If

                If var_auth = "1" Then
                    Dim pro As Process
                    pro = Process.GetProcessesByName("explorer")(0)
                    If pro Is Nothing Then
                        Process.Start("c:\windows\explorer.exe")
                    End If

                    'Try
                    '    pro = Process.GetProcessesByName("explorer")(0)
                    'Catch ex As Exception
                    '    Process.Start("c:\windows\explorer.exe")
                    'End Try

                End If

            End While

this code is written in backgroundWorker's doWork() event.

my windows service will check for a value in xml database, if its 0 then it will check if explorer.exe is started or not, if yes than kill it.

if the value in xml file i found 1 than it will check if explorer.exe is started or not, if not than start it.

Problem : when i start the service, it kills the explorer.exe once, but explorer.exe open automatically and the service fails to kill it again.

Error : Accecss is denied.

if its some permission problem than how would it killed first time ??

Is there any problem with the code ???