desktop pc bias and driver errors?

getting check sum error.. bias will only load defaults..so can not use PnP system..also audio device not working..finds new hardware on boot up but only searches optical drive for drivers..a pci device is yellow flagged in manager !!! says Microsoft uaa bus driver for hd audio..but I can not get it to go on-line to find a driver..this is a fairly new build and did work 100% at first..any help would be very welcome !!!