You can find GK2 on GOG, optimized to run on newer OS platforms, for $5.99.
http://www.gog.com/en/gamecard/gabriel_knight_2_the_beast_within
Each Gabriel Knight game is the pinnacle of that adventure gaming period to me in storytelling, gameplay, and all around execution.
GK1 - VGA graphics
GK2 - FMV
GK3 - 3D