Multiple keypresses?

I am making a game (an FPS), and as is it works fine on my system. But it uses sometimes up to 3 keys at one time. I could change this but the control would not be as nice as it is now. The keys it uses are shift and any combination of the arrowkeys. The shift key is just for a boost in speed, and/or rotation. I love the was it feals being able to power into sharp turns. What I am asking is...

1. What can it do to keyboards that don't suport more than one key press at a time.
2. Is it still bad to use a combination of the mane part of the keyboard with the arrow keys, or are the arrow keys designed to be used this way?
3. Is there a way to detect if a keyboard can handle multiple keypresses? Perhaps I could make a second system for those keyboards.

Personally, I have never had a system that didn't let me use multiple key presses at a time..

All my programs (projects) require the use of the Ctrl or Shift keys with other keys and it has worked fine on every system I have tested on..

Just my 2 cents

Never heard of one.

Irrelevant. All keys are equal (but just have different scan codes).

It's always a good idea to let the user define their own keys if they wish...

Hmm. I guess I won't worry to much about it then. The thing is, I posted a game I was working on when I first started learning blitz, and was told that by several people, including blitz support.
Well thanks for the input.

Note that a lot of keyboards can't handle more than 3-4 keys pressed at the same time. That's what you may have been talking about.

What WolRon said.

I've had two keyboards that wouldn't send the second keypress if two cursor keys were pressed at the same time.

They are both up on the shelf behind me.

I was wondering about this too. Does anyone know what brands of keyboard can handle more than 2 keys at a time, because mine can't with certain combinations. Maybe it's because I have a keyboard that came with my computer.