UnauthorizedAccessException: Access to the path 'C:\' is denied.

Cant figure out why i'm getting this exception, my c:\ disk has complete read/write permissions for all users and running UNITY as an administrator does not help so I assume its not a permissions issue. full error:

UnauthorizedAccessException: Access to the path 'C:\' is denied. System.IO.FileStream..ctor (System.String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, Boolean anonymous, FileOptions options) (at /Applications/buildAgent/work/c514da0c8183631c/mcs/class/corlib/System.IO/FileStream.cs:259) System.IO.FileStream..ctor (System.String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize) (wrapper remoting-invoke-with-check) System.IO.FileStream:.ctor (string,System.IO.FileMode,System.IO.FileAccess,System.IO.FileShare,int) System.IO.File.Create (System.String path, Int32 bufferSize) (at /Applications/buildAgent/work/c514da0c8183631c/mcs/class/corlib/System.IO/File.cs:135) System.IO.File.Create (System.String path) (at /Applications/buildAgent/work/c514da0c8183631c/mcs/class/corlib/System.IO/File.cs:130) System.IO.File.WriteAllBytes (System.String path, System.Byte[] bytes) (at /Applications/buildAgent/work/c514da0c8183631c/mcs/class/corlib/System.IO/File.cs:594) Program.Start () (at Assets/Scripts/Program.cs:28)

code:

 using System;
 using System.IO;
 using System.Net;
 using UnityEngine;
 
 public class Program : MonoBehaviour
 {
     public void Start()
     {
         System.Net.ServicePointManager.ServerCertificateValidationCallback += (s, ce, ca, p) => true;
 
 
         // Create web client simulating IE6.
         using (WebClient client = new WebClient())
         {
             client.Headers["User-Agent"] =
             "Mozilla/4.0 (Compatible; Windows NT 5.1; MSIE 6.0) " +
             "(compatible; MSIE 6.0; Windows NT 5.1; " +
             ".NET CLR 1.1.4322; .NET CLR 2.0.50727)";
 
             // Download data.
             byte[] arr = client.DownloadData("https://docs.google.com/file/d/0B_jZsNBM3OCeX21oaEZzUTh0enM/edit?usp=sharing");
 
             // Write values.
             Debug.Log("--- WebClient result ---");
             Debug.Log(arr.Length);
 
             File.WriteAllBytes("C:\\", arr);
         }
     }
 }