Hi Rao
Kindly follow the steps to install the new Trex instance on Windows 2012
1. On exiting Trex server Take the backup of Indexes by using the 'ExportManager.py" as mention in the SAP Note 975965 - TREX 7.0/7.1: Data backup (online) and recovery
2. Install the new Trex instance in the Windows 2012. http://scn.sap.com/docs/DOC-43539 (This link describes for Linux but it will be useful for windows as well)
3. Trex configurations as per your requirement http://scn.sap.com/docs/DOC-43539 (This link describes for Linux but it will be useful for windows as well)
4. Restore the Trex backup as per the SAP Note 975965 - TREX 7.0/7.1: Data backup (online) and recovery
Thanks & Regards
Ram