In my opinion it's a software issue. Why? because on my keyboard some oilder DOS game have this problem (such as Mortal combat 2 where you can't opress more than 2 key at same time or Super Karts also have some problems). I also noticed that in need for speed 1,2, 3 and 4. when i press the "H" key (horn) at steer left at same time the wehicle wont turn. However if i change the horn key to let's say "Q" it all works perfect. Some keys just don't go well together in some software.
Another proof thta this issue is software related is that when i play Half life or new Windows games (Medal of honour, Return to Castle Wolfenstein etc.), or some old ones, such as Space Federation, i don't have this problem. i can press a lot of keys at same time yet the keybord works fine. for example in Half life i press jump+crouch+reload+forward+slide and it all works without any problem.
therefore it is clearly a software issue known as Key-jamming. often two keys have same or at least simmilar address. so when you press them at same time they produce a beep in computer- some old dos games used to have it but many new windows games have this issue solved.
solution (if possible) is to change the keys you are playing with. to which ones? well you will have to do a bit of testing to find that out but left arrow+H is no good.
