If someday in Quark 6.6 beta 7, when you double click a .qrk, .qkm, .bsp or .map file and windows 7 ultimate doesen't allow by default to open these files with Quark, go in regedit and delete the below instance (with its regedit Quark folder) :
Next time when you double click a .qrk, .qkm, .bsp or .map file, windows
7 ultimate will ask you again to choose a default program. Choose alway
open with, at your Quark.exe and will work, the above instance will
write itself in regedit.