theres a halflife inf file
for win2k
normally that is used if halflife doesnt even start in win2k
but i thought i would just ask u if u have the inf file installed
just a thought
another thing is i sometimes used to have progs runnin opengl in halflife but i fixed it unfortunately dont know how
was long time ago
so maybe try runnin it in d3d if u have it runnin opengl