package 'manifest designer package' failed to load Windows Phone SDK 8.0

I am very new to Windows Phone Development therefore I do not know much about it....

I installed Visual Studio 2012 in my Windows 8.1 64x Operating system after installation I downloaded Windows phone sdk 8.0 iso and installed it too ... 

I watch tutorial and performs those steps , one of those tutorial's steps to double clickWMAppManifiest.xml to change the icon of Windows Phone Apps  but When I double Click On this it gives following error

package 'manifest designer package' failed to load

and Also AppManifest.xml  is not loading and it gives this error

Visual Studio has encounterd an unexpected error

i have uninstalled all and re-install al of this including sdk and vs2012 but still it gives error not in one project but each time I tried to goto NewProject and selectwindows phone App  and without doing anything I tried to open those files but it gives error

Please Help me .... 

Hi This is Syed Azy