Web applications are being executed in sandboxed environment which prevents damaging the host systems. Your files can only be accessed if they are placed under the root directory configured for your site. For the location of the file in your host file system, you can call the method
MapPath
:
http://msdn.microsoft.com/en-us/library/system.web.httpserverutility.mappath.aspx[
^].
And, come on, you server host may have no the idea even on what the "drive C:" is :-).
—SA