From Just Solve the File Format Problem
INF, or Windows Setup Information File, is a kind of INI file used by Microsoft Windows to control the installation of drivers and other software. Though it looks like a configuration file, it is used more like a setup script.
In addition to .inf format, there is a .pnf "Precompiled INF" format, and an .inf_loc format that reportedly contains cached information.
A standard INF file has a "[Version]" section, containing an item named "Signature". But note that some INF-like formats, such as Autorun.inf, have a different structure.