Start up problem
Hi Irmf,
Generally, that loud beep you hear is your BIOS (the part of the computer that turns on everything else) alerting you that there is a serious error with it's ability to function. Just for example, the beep could be due to your RAM not being properly seated, your BIOS being damaged or missing, your Hard Drive not being detected, or a non-system boot disk being inserted.
So troubleshooting that particular problem sounds tricky. But I do have a few possible repairs you can attempt that would at least let you know why it is making these error beeps, and go about seeking repair assistance.
1: Remove your RAM from your unit. On the bottom of your computer, you will find one or more small covers that are easily enough unscrewed to allow you access to some of the internal parts of the machine. Underneath one of these panels will be (usually) two thin white slots arranged either back-to-back or stacked as a staircase one on top of the other. These are the DIMM slots for your computer, and should contain your RAM (the green small rectangular circuit boards that contains your your temporary memory). You can release the pressure release on both sides of each stick, and lift up gently to remove the sticks of RAM. The RAM is removed and replaced by inserting it firmly into the DIMM slot at approximately a 45 degree angle. You may only have 1 stick of RAM, but what you need to do is alter the configuration of what you have. Such as: Remove both sticks of RAM if you have two, then only place one into the machine and attempt to turn on. If it does not turn on, repeat by removing the 1 stick and replacing it with it's sister stick. Test and see if it works / shows any improvement. If you have 2 RAM sticks, one might be bad and you can determine if it is by testing both and eliminating each as working or not.
2: If removing your system RAM and replacing it firmly into your unit does not chance the condition at all, next I would suggest attempting to connect an external monitor to the laptop and perhaps producing a video output. Your laptop should have a VGA connection (usually blue, has approx. 15 pins, and is shaped like a trapezoid). Also, your laptop should have a Function key (the F-numbered keys on top of the keyboard) that enables you to switch the video output from the laptop screen to an external CRT or LCD. Usually this is F4, F6, or F8. It should say CRT/LCD or have an image of two rounded squares on it, in blue painted decal, underneath the F-1-12 part of the key.
This might allow you to determine that your screen is bad, and perhaps it will mention why. Lots of possible error messages with that, if it works at all.
3: You can remove the casing from the laptop if you are very careful to notate where each screw is removed from so that you can re-assemble it afterwards. Locate the CMOS battery on the motherboard (it looks like a larger, flat, watch battery). If you remove this, and place it back into the motherboard, you can often cause your BIOS to reset (potentially removing an improper BIOS setting or update).
Otherwise, you are limited to what you can do yourself without the use of full technical manuals and equipment to test the integrity of individual components in the laptop to figure out why it won't post at all.
My personal guess, is that it is a motherboard issue, but saying 'it's a motherboard issue' without attempting some troubleshooting first is almost a cop-out if you're a tech. If it has a warranty, I would suggest having HP repair/replace parts on it under your coverage rather than attempt to solve this yourself, but the steps I've outlined are to the best of my knowledge how you would eliminate possibilities that could be related to your error and no display.
Sorry for the length of the post, but I hope that helps!