There could be a couple of options here: 1. The keypad is defective in which case you need to replace it. 2. The keys are sticking which will cause this problem and is quit frequently what happens (unless all your keys are doing this in which case it will not be the problem as not all keys stick at the same time unless something has been spilled on the keyboard) 3. You might need to update the drivers for the keypad which you can download from the manufacturer's website
. I do not think you have a virus because you would notice other things happening to your operating system or hardware. Since you plugged the usb keyboard in and it worked just fine, I think your keypad needs replaced, which you can order from the manufacturer as well and they are not that expensive. You can try downloading the drivers first and see it that corrects the problem or try removing your laptop face plate and cleaning your keypad, just be careful with the plastic tabs that hold the face plate on and not break them. I am pretty sure your keypad is bad. Please let me know if this helps or you need further assistance.
If you would not mind rating my help, I would really appreciate it. Thanks