I recently bought a ASUS M5A97 LE R2.0 and got it to run with a gt640. A problem occured when I tried to out my other graphics card in which is a gtx 750 ti. When I use the gt 640, the boot goes smooth. When I use the gtx 750, all usb seem do not want work after about 3 seconds of the boot screen. I've tried turning off Fast boot, but that changes when different hardware is installed. I've been stumped for a while and would appreciate the help.