This is what texture files look like

[=Omni=]

The GrumpyOldMan in this thread has written how to convert the texture files to dds ones. However, we can only conver them to dds, but not back, hence you cannot make any modifications to them.

How to do it?

1. copy the file!
2. open the texture file in hex editor
3. delete the first 48 bytes (if you don't want to count the bytes, just delete everything until it's written DDS (IN CAPITALS!;first one - in the beggining of file, and NOT in capital letters has to be deleted)
4. rename the file from texture to dds
5 And Voila!