Cannot load CTB in Plot Style Table

[newbie]

I cannot load any CTB files in the Plot Style Table in my Page Setup. AutoCAD only allows me to select/set-up STB files. My Plot Styles directory has both CTB and STB, however, AutoCAD is only allowing me access to ".stb" files. When I try to create a new Plot Style, it automatically saves it as a ".stb".

Any ideas on what's going on?

[Exxit]

CONVERTPSTYLES :?