laptop keypad interferes with external USB keyboard

I had a problem in laptop keypad interferes with external USB keyboard.

Basically, the external USB keyboard works fine, no prolem at all, always.

While the external USB keyboard is attached, the external USB keyboard works fine, But the laptop keypad had some problem:
(1) some keys work fine, (such as Q, W, E, R, T, Y, A, S, D...). These working keys are located on the left side of the keypad;
(2)while the external USB keyboard is attached. the keys on the right side do not work: if I press "U" key, I get "4" on the screen; if I press "I", I get "5"...


I have tried:
(1) unplug the external USB keyboard, restart the laptop, the problem is still the same;
(2) Still unplug the external USB keyboard, delete the keyboard from the control panel, restart the laptop, it does not work either!! After the installation of the keyboard, the keyboard properties have such devices: Standard 101/102-Key or Microsoft Natural PS/2 Keyboard; I tried another time, it has another device: HID Keyboard Device.

Can anyone identify what I can do to make it work?

Do both keyboards work at the same time, for you all?

Thanks. Hope I describe my problem clear.