read HTMLZ format Linux

i transferred my windows library to my Linux partition (dual boot windows 7, ubuntu 10.4) im using HTMLZ to prevent chapter "jump" (see this thread) but now i can not open my HTMLZ formats in the built in reader i have checked that the HTMLZ format is assigned under preferences/behaviour/use internal viewer, and removed all "open with" assignments for HTMLZ files in Ubuntu. what did i break this time and how do i fix it?

thanks
Phoenix


P.S. yes i know 10.4 is OLD but i HATE the unity desktop