Today keyboards have a small buffer, making the machine "forget" last keys pressed if the buffer if full. Try to get an old keyboard. I use one, and y can play with 3 friends using 7 keys each (didn't try more). I repeat, Newer keyboards do not support multiple keys pressed.

Yes and older keyboards like let's say ten year old keyboards don't have a buffer at all and just keep beeping at me when trying to do a 360° in GTA San Andreas Thx for the tip about the keyboard logic. When I remapped one of the keys I was able to do it

yeah, it sucks, i have a newer keyboard, and i can hold maybe a couple of letters, and it beeps at me over and over!

thats why I use an keyboard from 1980

evenif some people always bother: "OWTFGM YOU HAVE NO WINDOWS KEYY!!!!!1111oneoneone"

I simply offer the possibility to map the keys where you want. Just find a combination which plays good and you're fine.

I have two usb game pads

another way; try two PSP games pad with parallel port. At present I test with two, if it works with 4 there, I would make a workshop(studio).

I just found that any triangle on my keyboard, such as wa-s beeps, while as-d does not. Apparently any triangle beeps.

Try this in your code:
player.move_x = key_w - key_s;
player.turn = key_a - key_d;

See if that makes a difference...

Now I have only 1 USB gamepads... I broke one when playing virtua fighter evolution.

My hint is:
A) Make your game turn based
or B) Use the combination of keys for several actions:
for example: A turn left, S turn right, A&S move straight. There are multiplayer games in the web which work like that. Its fantastic, because they knew that problem but wanted to make a mega multiplayer game playable on one PC. That means, the used for player one keyboard, for player 2 keyboard for player 3 mouse and for player 4 joypad. The controls work like that: key 1 = move left, key 2 = move right, key 1 & 2 jump

That means the player with mouse can walk left when pressing mouse 1 and walk right when pressing mouse 2. When he presses mouse third (some horrible mouses have no third button - so they made the mouse 1 & 2 to jump) he jumps.