1. Go to C:\Program Files (x86)\Microsoft SQL Server\MSSQL10_50.FTVIEWX64TAGDB\MSSQL\DATA
2. Delete the modellog.ldf and the model.mdf.
3. Browse to the following folder: C:\Program Files (x86)\Microsoft SQL Server\MSSQL10_50.FTVIEWX64TAGDB\MSSQL\Template Data
4. Copy the following two files: modellog.ldf and model.mdf.
5. Paste the two files in the folder located at: C:\Program Files (x86)\Microsoft SQL Server\MSSQL10_50.FTVIEWX64TAGDB\MSSQL\Data
6. Reboot
7. Restart SQL Server(FTVIEWX64TAGDB) under services, if not started