Enable-migrations command produces "Could not load file or assembly..." Errors

I just migrated my Entity Framework from 5 to 6. Then when i tried to run Enable-Migrations command suddenly i got these errors:

Exception calling "LoadFrom" with "1" argument(s): "Could not load file or 
assembly 'file:///D:\BitBucketGit\packages\EntityFramework.5.0.0\tools
\EntityFramework.PowerShell.Utility.dll' or one of its dependencies. 
Operation is not supported. 

(Exception from HRESULT: 0x80131515)" At D:\BitBucketGit\packages
\EntityFramework.6.1.3\tools\EntityFramework.psm1:780 char:5 +     
$utilityAssembly = [System.Reflection.Assembly]::LoadFrom((Join-Path 
$ToolsP ... + 

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

+ CategoryInfo          : NotSpecified: (:) [], MethodInvocationException
+ FullyQualifiedErrorId : FileLoadException


You cannot call a method on a null-valued expression.
At D:\BitBucketGit\packages\EntityFramework.6.1.3\tool 
\EntityFramework.psm1:781 char:5
 +     $dispatcher = $utilityAssembly.CreateInstance(

 +     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo          : InvalidOperation: (:) [], RuntimeException
+ FullyQualifiedErrorId : InvokeMethodOnNull

Exception calling "CreateInstanceFrom" with "8" argument(s): "Could not 
load file or assembly 

'file:///D:\BitBucketGit\packages\EntityFramework.5.0.0\tools
\EntityFramework.PowerShell.dll' or one of its dependencies. Operation is 
 not supported. (Exception from HRESULT: 0x80131515)"
 At D:\BitBucketGit\packages\EntityFramework.6.1.3\tools
 \EntityFramework.psm1:809 char:5

  +     $domain.CreateInstanceFrom(

  +     ~~~~~~~~~~~~~~~~~~~~~~~~~~~

  + CategoryInfo          : NotSpecified: (:) [], MethodInvocationException

  + FullyQualifiedErrorId : FileLoadException

After googling,some suggested to imply a full trust on the package folder which i did. But the error remains.

Is there any other way i can make it fixed.

cheers,

John

Thank for any help. Actually i just found the answer by changing the devenv.exe.config files.