Currently I'm working on a TPC to TGA converter, and I'm having a bit of a problem - the 'encoding type' field in the header seems to have very little to do with the actual encoding type in the file. It handles the DXT1 textures I had been throwing at it fine, and I've written DXT3 support (DXT5 to come - I don't think I will need support for the premultiplied formats DXT2 and DXT4), but, I don't know... look at ip_lightning and lbl_levelup for example. I will continue to look into it.
aveeare: Thanks for the information. I've been referring to the MSDN DXTC docs, but I didn't notice any references to a 4444 or 1555 color format.
As for testing with D3D, well, I'm more comfortable with GL since I've been a Windows user for a grand total of 2 weeks in this century, but I've definitely been considering it (provided I can get the DX SDK to actually work with MinGW).
Edit: Oh yeah, and it also doesn't help that I goofed my pitch calculation... at least I can read those big mainmenu textures now (2048x1024) =)