Acceleration problem of all kind of games!

hi friends i am very upset due to amazing issue.. 1st sorry for my english.
problem is.. whenever i play any game like nfs underground, most wanted, or i play GTA4, GTA san anders or any other game.... when i push the button for accelerate (UP key from the arrow) and as i turn it into right or the left, the acceleration get stop and when i push again the Up arrow key it starts fine.. then again as i push any key to turn car right or left, it again stop and then have to push again UP button for acceleration.... i have changed the key setting from aero key to other keys (like wASD) but problem is not solving any help will be thankful

my spect is.. core 2 dual 2.21, 1 gb ram, 160 gb hard, nvidia 9200 card.

thanks

sounds like a keyboard programming issue, just to be sure have the acceleration on "z" and brake "x" and then right and left on normal keys