added Radeon R7 250 to a HP Pro 3400 and get no video on the monitors nor does the machine seem to be booting at all since i cannot access it remotely either. The computer has a i5-2300 processor with 8GB RAM. It has Intel H61 Express Chipset. It boots fine with onboard video.
Good day Smorgan,
Does Windows recognize the Card ?
Which Driver version did you install ?
A CGAX-R7256LM4 takes about 60 Watt of power, does your system/psu have that power available ?