chris987 :
thats why i suggested a gtx 750ti cause it doesnt require supplementary power and wont trouble your no good psu. make sure the gpu is securely fit in pcie socket. some pressure is required to do so. make sure you plug in monitor cable in gpu and not mobo.
I've tried again. I get the HP Blue screen with Press Esc for Menu, and a beeping sound every now and then. Finally, the screen goes black and I see the monitor's message No Signal.
I got this from the internet: 'When there is no video signal reception from the processor, the monitor displays the NO SIGNAL error message. The reasons can be due to a hardware component failure... The system makes a short beep error representing an issue when the monitor is connected. The system crash prevents the monitor to display anything. The computer is now unable to boot. No signal can also be a graphics card issue. It is recommended to use a separate power supply to eliminate low power supply to the monitor.' Perhaps, I do need the PSU connected to my GPU, after all.