hi everyone

ok here goes, i have a problem with my boot up process, one of these three things happen upon start up, 1. i turn on the pc and nothing happens but i can hear the pc so i know its actually turned on?....... 2. i turn on the pc and i get a bios checksum error and it tells me to insert disk drive media floppy? .........3. i turn the pc on and it takes me straight into the windows options with safe mode, start windows automatically etc....., and wen i try to start windows manually it freezes at the point where u get the black screen with the windows icon and the blue loading bar, but sometimes it gets passed that and a disk check starts up and loads windows sometimes?