Computer not talking

Hi there,

My computer is suddenly not sending an output to my two monitors, mouse and keyboard. It was working fine yesterday. Have taken a look inside and nothing seems loose or damaged, have had a new graphics card (xfx r7800) put in last year, and new memory drive. Have scoured forums but no one seems to have had this particular issue (in that there's a sudden onset without there being a new piece of kit put in very recently)

Please help!