This is possibly the most frustrating problem whenever I build a new pc or reinstall Windows but after turning it off and on a million times it normally magically starts working again however this time it really doesn't want to. So recently built new computer took my HDD and power supply from my old pc everything else is new. My OS was on my HDD so it boots up without having to reinstall this is when the problem starts can't use mouse and keyboard on login screen. I should note it's windows 7. So tried every usb port on the computer to no success. Tried booting in safe mode and no success. Went into to BIOS (motherboard is ROG Strix b450-F) keyboard and mouse works enabled all USB ports enabled legacy usb support, restarted no success. Powered down computer unplugged from socket waited 20 mins, no change. Decided to just reinstall Windows plugged in my bootable usb get to language screen... can't use kb/m. From what I have seen the only options I have are get a ps/2 mouse and keyboard but really don't want to have to wait for them to arrive or get windows 8 which apparently has the drivers I would need built in. Apart from these solutions does anyone have any other ideas? I should note that as I moved my HDD to the new motherboard it will have my old motherboard drivers on it could this be interfering with it? If so is there anyway to uninstall these drivers from BIOS