Is there ever a display if you retry a few times? Not entire boot-up screen but maybe the bios or HP logo for a short time, then it disappears and etc. to continue to boot. The kybd. should flash for a short time as well, but if it doesn't then you got a deeper problem.
What, i always do is try yet another bootable disc. Burn one if you like, I suggest the "live version" of Ubuntu, burn it's .ISO to make bootable. Assure the 1st boot device is CD/DVD drive or select it from the boot menu. If you don't still get a display, test monitor elsewhere. It always helps to state the full details of HP model#, not HP PC, we don't even know if its laptop or desktop, etc..
I've got an interesting situation with my PC (HP, Win7 home premium, 64 bit, 8 Gb memory).
I turned it on. The light indicating the HDD flickered for a while, then went out. No start screen, no Starting Windows screen. The fans are running, the indicator lights on some PCI cards are lit. The keyboard is not lit up, either. I checked the cable connections to the mother board, and the powersupply connections. All are good.
I shut the PC down, replace the drive with a recent clone (less than a month). Similar results.
I pulled the clone out, and installed it in an older Win 7 machine, and it booted fine (as expected, it was updating hardware, etc), but the drive definitely worked.
I looked to see if any connections were disrupted when removing the drive cage, but there really isn't anything in the way of it. I tried a different SATA connection point, but this also didn't give me positive results.
At this point, I'm stumped on what the problem might be.
Any clues to help me look into this further would be helpful. Thanks.