Assuming you installed PostgreSQL on Windows with the PostgreSQL "One-click" installer packaged by EnterpriseDB, psql is not added to the PATH automatically. That's partly because adding it to the path could otherwise cause confusion when people have multiple versions of PostgreSQL installed.

You need to specify the full explicit path to psql, eg:

"%PROGRAMFILES%\Postgresql\9.2\bin\psql.exe"
or add psql to the user PATH environment variable, see eg this guide.