unable to install and configure office web apps in WIN OS 2008 R2 SP1

hi,

 i am trying to set up  Office web apps on a server, and when i try to execute the powershell

i have gone through the steps mentioned in the below url :

http://stevegoodyear.wordpress.com/sharepoint-2013-build-guide/office-web-apps-2013-server-install-and-configuration/

when i tried to run the powershell command :

......

On the first server for the Office Web Apps farm, execute the following PowerShell command to provision the farm:

New-OfficeWebAppsFarm -InternalUrl "https://office1.contoso.com" -ExternalUrl "https://office.contoso.com" -SSLOffloaded –EditingEnabled

am getting the error 

New-OfficeWebAppsFarm : The operation failed. The server did not meet the following prerequisites:
- Windows Update KB2592525 must be installed.
At line:1 char:1

so, i tried to install the KB2592525 , and i   got another error message :

"this update is applicable to this computer" .

my server is win os 2008 R2 SP1.

so can any one help me to know and next step why that kb is failed to install and update and why my powershell command failed.