Keyboard and mouse not responding after removing gpu and adding new cpu win8

if you have keyboard control in BIOS, see if you can get into windows safe mode by hitting F8 a bunch of times before you lose keyboard control. See if you get keyboard function in safe mode, then remove your old graphics drivers if you can.
I assume you are using a USB mouse/keyboard. if you can not get it to work try the old ps/2 type connector if your motherboard will still support it.
-if using USB, remove any extra USB devices from the USB host (mainly anything that is charging like a IPAD, also, make sure you are connected to a standard USB port )