ACS 4.2 doesn't support windows 2012. The last windows OS it works well was 2008 NON-R2. Since ACS 4.x is now EOL, was End of Software Maintenance as of October 26, 2012 we can't even file enhancement request to support windows 2012 as a backend database.
The support for Windows 2012 has been added in ACS 5.4 patch 2
ACS 5.4 patch 2 supports Windows 2012 AD.
http://www.cisco.com/en/US/docs/net_mgmt/cisco_secure_access_control_system/5.4/release/notes/acs_54_rn.html
~BR
Jatin Katyal
**Do rate helpful posts**
~Jatin