Problem using ps2 keyboard with inspiron 8200 - please help

I have been using an oldish ps2 keyboard as i have had to also get a new monitor as the one on my laptop failed, so i now use the laptop basically as you would a normal computer with everything connected into it.

 

When i try and play fps games i have noticed that when running, pressing W and jumping at the same time pressing space bar it will then stop running and i will have to take my finger off the W key and put it back on again, something that i didnt have to do when using the laptop keyboard. i have tried using other buttons for run and jump aswell and they all do the same.

 

Also the \ key does not work on the ps2 keyboard.

 

Is this because the keyboard is old, or is there a way around this. Thank you in advance.