This is the error I am getting is
crogramData\Autodesk\RME 2012 Templates\US Imperial\Mechanical-Default.rte
I have already tryed to do this, add content us imperial content to my revit 2012 mep software 2 times from this option below. Uninstall or change a program, select the Revit application, and click Uninstall/Change.
I have also updated revit 2012 mep with the newest service pack 2 from here
We are using windows 7 64 bit operating system
Post this issue in the Installation & Licensing forum. It's more likely that you'll get a response there.
The first thing to do would be to verify if the Mechanical-Default.rte file is located in the folder specified (C:\ProgramData\Autodesk\RME 2012 Templates\US Imperial). If the file exists in the folder, verify if you can open it directly.
If the file is missing from that location, you could also try doing a Repair on the installation (through the Control Panel).