Exchange 2007 and 2013 Coexistence-- Schema update issues with Server 2008

Hello- 

My organization is attempting to have a 2007/2013 Exchange coexistence.

The current 2007 Exchange deployment is on Server 2008. I've patched it up and it should be ready for the AD update.   (However, I'm getting the error below)

C:\Users\Admin\Desktop\Exchange>setup.exe /PrepareSchema /IAcceptExchangeServerLicenseTerms 

When I run this, I get the following response. 

"An unsupported operating system was detected. Exchange Server 2013 Client Access
and Mailbox Server roles support Windows Server 2008 R2 SP1 or later and Windows Server 2012."

Any suggestions?  I can't find much about this. I do not think the AD prep

Thank you