XeNTaX

Anybody familiar with a PSP image file format that uses the magic bytes "xt." (0x78742E00)? These files were packed into a lump file and were extracted using a TOC, but there was no file name, so I don't know the extension.

My goal is to be able to convert these to an editable image format so that I can edit and repack these files. A sample of this kind of file can be found here:
http://www.mediafire.com/download/7srrhthliljpyjl/344

Any information is appreciated.