|Not enough info.|
Which video card did you have prior to the HD4350? Was it an actual card or was it onboard video? Did you uninstall the old drivers before installing the new card? If you were using onboard video, did you disable it in the BIOS? change the shared memory amount to 'none'? set the 'initial display 1st' setting to PCIe? Are you sure the card is fully seated in it's slot? Are you getting any beeps at startup? Do you have the monitor connected to the new card?