keyboard and mouse not responding

I have searched through some of the messages on keyboards and mouses not responding and have not been able to fix the problem.  Because both the keyboard and mouse are not responding I cannot sign into the computer making it impossible to go any further with the process of trouble shooting the problem.  HELP! anyone have any ideas of what is wrong.  So far I know the mouse has power, the keyboard does not, but it does work on another computer.  I have tried rebooting and unconnecting then reconnecting them both and tried hooking up a wireless mouse and keyboard.