[2005] streamWriter giving error 'Access Denied' to files created already

[Icyculyr Fr0st]

If I have

Private Sub myform_load(byVal sender As Object, byVal e As EventArgs) Handles MyBase.load
Dim sw As New StreamWriter("myurl") 'this will create file in debug folder
sw.write("Sup yo")
sw.close()
End Sub

If I run that again, will that erase the previous file created? or will it just edit it and write 'Sup yo' in it?

If so can someone tell me how to write to a file that exists already?