You cannot turn on your PC. You could not open a CD ROM drive and kept pushing a blue button to turn it off but it would not. Then you unplugged a power cable and replugged it into a wall socket.
Still after pushing a power button it would not come on. You can unplug a power cable from wall socket and that computer. Press that computer's power button for a minute.
Plug back power cord into wall socket and computer and see if it will power on. You can try using a different wall outlet. If your up for it, I can walk you through reseating some cables and performing some troubleshooting steps.
This would require you opening that computer case. When you plug it into the wall outlet and press a power button do any lights at all turn on, even lights on the back of it? Please follow these instructions for opening the PC case of your HP computer.
You need to only remove the right side panel. Once you remove that right side panel, you wan't to disconnect the large power cable from the power supply from the motherboard. Disconnect a power cable from a wall socket too.
Press the blue power button on front of that computer for a minute. Plug power cable from power supply back into motherboard, then plug power cable back into wall outlet and try to power on that computer. You might have to press a blue power button for a minute to drain any electricity.
Press blue power button for a minute to drain any electricity. Plug power cable from power supply back into motherboard, then plug power cable back into wall outlet and try to power on that computer.? I think most likely that computer has a bad power supply.
You could try unplugging as many devices as possible, ie hard drive, cd-rom drive, floppy, memory, etc. to see if it is a failing component. Do any fans turn on or does that computer beep at all? You don't have to wait a minute if you unplug any of those hardware device power cables.
Yes, you can test one at a time to try to narrow down what device might be failing. You can try unpluggin all those white power cables except motherboard one and see if it will power on. Unplug all the smaller white power cables from their devices ie hard drive, cd-rom, floppy drive.
Those would be ide cables. You can unplug it as well. Well it is possible it is a bad motherboard or power supply.
The memory is located right next to that large white power motherboard cable. I recommend taking it to a computer repair shop so that they can diagnose it fully. Some might diagnose it for free.