It's pretty unlikely that your mouse and keyboard got damaged at the same time. Test them on another computer to make sure. Why did you unplug them in the first place ?
What's the brand and model of your computer ? If it's a custom build then what's the motherboard's brand and model ?
When you turn the computer on with the keyboard attached you should see the 3 little lights (num lock, caps lock, scroll lock) flash once. If nothing happens then there's a problem with the keyboard or the motherboard.
Try to enter the BIOS at startup (repeatedly press del or look for some "press xx to enter setup" message), if your keyboard responds at that time then the problem is related to Windows.
See if you can borrow an USB keyboard and mouse from some friend and test your computer with them. If an USB mouse or keyboard works but a PS/2 one doesn't then there's a problem with the PS/2 ports on the motherboard.
Do you get a "keyboard error", "keyboard not found", "no keyboard present" or similar message at startup ?