The addons in the Res\AddOns folder are not third-part addons they are original addons, installed with Resistance.
O.pbo contains the Resistance objects and their textures.
O_WP contains Resistance weapons including:
Glock
Ingram
Remington
S&W
and associated optics etc + textures
KOLO appears to be the bicycle, and rider, plus textures, but dont quote me on that.
You will probably need to re-install Resistance and subsequent patches for Resistance if they are missing.
Planck