There are 4 key components in your PC:
If you have issues with one of them, the PC won't POST (power on self test) and you won't hear an audible beep when the PC is turned on. If you're not getting the POST beep, your issue is one of those components.
I've seen a lot of surged PCs like either unplugging the box itself for an hour or so or unplugging the box AND power connectors from the motherboard. Give it an hour or two and then plug everything back in. Certain model HPs respond well to that.
Beyond that, the best troubleshooting is swapping compatible components into a machine that can accept them, and narrowing it down to the one component in the POST list that stops it from booting. THat said, most PCs will attempt to post and display video output with no RAM, so I wouldn't start there.