i can confirm this, game works properly on my 386 with both numlock settings.

i can confirm this, game works properly on my 386 with both numlock settings.

in winxp this game works properly only with turned off numlock

this game i guess tries to lock numpad off and while it succeeds on 386, it doesn't succeed in winxp, hence the difference in 386 vs winxp behaviour. and also explains why it doesn't work in dosbox

The problem of dosbox is that in dosbox's command line i can modify numpad behaviour with shift when numlock is on, but i cannot do it when numlock is off (on my 386 and in winxp i can always modify numpad's behaviour)

edit:
that would be true if it was working in windows with numlock on, anyway the solution may be caused by dosbox's numpad not working properly with shift

so with numlock off, shift works as if numlock is pressed on your 386 ? Got to check how I coded that part in dosbox.

edit: at first glance it looks like either shift or numlock toggle the shift values.
So that is alright ? The only part missing is the cancelling when they are both there.

Does your keyboard generate extended keypresses ?

on 386
with numlock off, shift works as if numlock is on
with numlock on, shift works as if numlock is off

anyway when testing dosbox and 386 in "star control 2" keys.exe both look different way: in dosbox i see numlock pressed when it is on, while on 386 i see numlock only for the moment when it is being pressed,
also when i press arrow keys i see as if i pressed both: shift and arrow (depending whether numlock is on or off)

that numlock always pressed is to work around a problem in sdl. it should go off once you press another key.

check my edit.