On my Athlon XP 2400+, setting CPU cycles to 7500 strikes the right balance between playability and non-stuttery sound. Any higher you lose sound quality, any lower you get too low FPS in space. Joystick and mouse don't work, but just playing it with it set to Keyboard (Options from Main Menu) works …

I get the same problem. My game also crashes when I try to land on the concordia, and I know my copy of WC2 is good. Have you guys ever considered that maybe the Concordia just isn't giving you permission to land, and is segfaulting you on purpose? Its pretty clear to me the programmers envisioned …