Keyboard stopped working computer locked

ok so a few nights ago i shut my computer down and went to bed.  got up the next day and tried to log on and my keyboard was not responding.  it was the factory keyboard and a bit old so i guessed it was probably bad.  well i bought a new one that is usb and it too will not work..  I cant get it to type to put in my password so i can log on.  I can open the F2 and F12 and both keyboards will work in those menues and attempt to go to safe mode but it asks for a password in safe mode as well and i cant type anything.. i am not sure exactly what type of dell i have but my os is xp.  please someone... any ideas?