What version of Windows? What brand model mouse/keyboard? Custom built PC (if so, what components?) or Prebuilt (if so, what brand/model?)
Instead of destroying more components...the easiest thing to do would be to test the devices on another PC. If they do the same thing - then you know it's an issue with the mouse/keyboard. If not, then it's an issue with the PC.
If you wanted to see if it's an issue with Windows...then download an Ubuntu LiveCD from The leading OS for PC, tablet, phone and cloud | Ubuntu
Burn the ISO to a CD or make a bootable USB drive with a tool such as Rufus, and then boot into the Live environment. If you have similar issues inside Linux, then it's most likely hardware issue with the PC. If it doesn't have the same issues, then it's most likely a Windows software issue (either something with Windows itself or a driver issue).