Error Msg 6522, Level 16, State 1 Receives When Call The Assembly From Store Procedure To Create A Text File And To Write Text

Hi,
I want to create a text file and write to text it by calling its assembly from Stored Procedure. Full Detail is given below

I write a code in class to create a text file and write text in it.
1) I creat a class in Visual Basic.Net 2005, whose code is given below:
Imports System
Imports System.IO
Imports Microsoft.VisualBasic
Imports System.Diagnostics
Public Class WLog
Public Shared Sub LogToTextFile(ByVal LogName As String, ByVal newMessage As String)
Dim w As StreamWriter = File.AppendText(LogName)
LogIt(newMessage, w)
w.Close()
End Sub
Public Shared Sub LogIt(ByVal logMessage As String, ByVal wr As StreamWriter)
wr.Write(ControlChars.CrLf & "Log Entry:")
wr.WriteLine("(0) {1}", DateTime.Now.ToLongTimeString(), DateTime.Now.ToLongDateString())
wr.WriteLine(" :")
wr.WriteLine(" :{0}", logMessage)
wr.WriteLine("---------------------------")
wr.Flush()
End Sub
Public Shared Sub LotToEventLog(ByVal errorMessage As String)
Dim log As System.Diagnostics.EventLog = New System.Diagnostics.EventLog
log.Source = "My Application"
log.WriteEntry(errorMessage)
End Sub
End Class

2) Make & register its assembly, in SQL Server 2005.
3)Create Stored Procedure as given below:

CREATE PROCEDURE dbo.SP_LogTextFile
(
@LogName nvarchar(255), @NewMessage nvarchar(255)
)
AS EXTERNAL NAME
[asmLog].[WriteLog.WLog].[LogToTextFile]

4) When i execute this stored procedure as
Execute SP_LogTextFile 'C:Test.txt','Message1'

5) Then i got the following error
Msg 6522, Level 16, State 1, Procedure SP_LogTextFile, Line 0
A .NET Framework error occurred during execution of user defined routine or aggregate 'SP_LogTextFile':
System.UnauthorizedAccessException: Access to the path 'C:Test.txt' is denied.
System.UnauthorizedAccessException:
at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
at System.IO.FileStream.Init(String path, FileMode mode, FileAccess access, Int32 rights, Boolean useRights, FileShare share, Int32 bufferSize, FileOptions options, SECURITY_ATTRIBUTES secAttrs, String msgPath, Boolean bFromProxy)
at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, ileOptions options)
at System.IO.StreamWriter.CreateFile(String path, Boolean append)
at System.IO.StreamWriter..ctor(String path, Boolean append, Encoding encoding, Int32 bufferSize)
at System.IO.StreamWriter..ctor(String path, Boolean append)
at System.IO.File.AppendText(String path)
at WriteLog.WLog.LogToTextFile(String LogName, String newMessage)