You must be here for Splatterladder HD pack.
Download z_hdet2.6.pk3.
After you downloaded you need to place into etmain folder.
If you using ETLegacy client you need to copy to
C:\Users\Yourprofilename\Documents\ETLegacy\etmain folder
If you are on a regular 2.60b client copy to
C:\Program Files (x86)\Wolfenstein - Enemy Territory\etmain folder
Or find your installation directory.
Thank you for Fragging.