Running fine and stopped at 37%. Permissions are good and everything seems fine. The install logs shows the schema getting set for exchange 2013 and then ...

Hi Joe,

Thank you for your question.

Did  you tell us more details which is about the steps of ADprep?

Did you post snapshot for us to troubleshoot?

In addition, we should update AD schema, then to prepare AD on domain controller by the following command(please notice order):

1.         setup.exe /PrepareSchema /IAcceptExchangeServerLicenseTerms
2.        setup.exe /PrepareAD /IAcceptExchangeServerLicenseTerms

We could refer to the following link:

https://technet.microsoft.com/en-us/library/bb125224(v=exchg.150).aspx

If there are any questions regarding this issue, please be free to let me know. 

Best Regard,

Jim