Numbers 0,1 and 5 won't work- why?

[dpshap]

I have recieved 2 refurbished Thinkcentre S50's and BOTH won't recognize 0, 1, and 5 from the number pad or the number keys.  Therefore, I can't enter in the Windows XP code to start up the computer.  I tried different keyboards and different input plugs in the computers, but nothing changes the problem.   Can someone help me?

[IPnaSh Guru]

What kind of interface have the keyboard? PS/2 or USB?

If it's PS/2, maybe the keyboard controller is damaged.

Also, you can use a Live CD (for example, Ubuntu) to discard any OS related problem.

Best regards.