My mouse and my keyboard both wont work. how can i fix that?

i turned on my computer and i noticed the screen stayed on sleep mode so when i looked i noticed the mouse light wasn't on nor the keyboard lights (ex caps,num lock). For some reason they just wouldn't work.They work fine on my laptop just not on my other computer. When i turn on my computer the keyboard and mouse lights do a quick flash and that's it. please help me