|If they are both PS/2 connected, the keyboard and mouse must be plugged into the proper PS/2 ports.|
The one for the keyboard is closer to the side of the case and is usually purple, the one for the mouse is farther away from the side of the case and is usually green.
If you are using an adapter (gender adapter) on the end of a corded keyboard or mouse cord to connect it to a different type of port, the keyboard or mouse
- must be a "combo" model - designed and wired up to be used with both types of ports.
- you must use the proper adapter - the one for a mouse is usually green, the one for a keyboard is usually purple.
If they are both USB connected, the USB controllers must be enabled in the mboard's bios Setup - they are by default but someone may have changed that. If that's disabled, you need to connect a PS/2 connected keyboard in order to be able to get into the bios.
Also, USB legacy devices or similar must be enabled in the bios in order for you to be able to get into the bios with a USB connected keyboard. That may or may not be enabled by default.
If they are corded, it's common for wires inside the cord to get broken after it has been used a lot, or after the cord has been yanked on at any time, often near where the cord enters the mouse or keyboard.
Try a different mouse or keyboard with your computer. Try your mouse and keyboard with a different computer.