Would you rather mean .tpc to .tga? Here is an extract from the general itro to modding tutorial, Getting started with modding: Tools + downloads (
http://lucasforums.com/showthread.php?s=&threadid=143421): ;)
Textures are located in ERFs -> Texture Packs. Texture Packs. The textures located in swpc_tex_gui.erf are best used for icons and portraits (for the party selection table) mostly and some other stuff as well.
The high - res textures are located in swpc_tex A
The med - res textures are located in swpc_tex B
The low - res textures are located in swpc_tex C
You'll find more details in the Skinning and Modeling tutorials (
http://lucasforums.com/forumdisplay.php?s=&forumid=595)