Ubutnu, huh? Sweet.I have 2 laptops older than that, windows will degrade over time for sure... that's why I took them and slapped Ubuntu on them. They run dandy with that OS.
Maybe, but not necessarily.It could be the video card too, but since it is an HP it probably does not have a separate video card and the graphics processor is built into the motherboard.
It might also be the hard drive, but probably not. Since you are not getting anything on the monitor even early in the boot sequence (before the hard drive is accessed) it almost has to be the motherboard.
So the bad news is you will need a new computer. The good news is the data on your hard drive is probably recoverable.
Does it beep and try to POST? Do you get ANY text at all. (memory test, etc.)?
If not, my money's on the power supply, especially with the noise. It could be another component (memory, processor, motherboard/BIOS), but the power supplys do tend to wear down and blow over time. I don't like the fact that it was actually ON and acting up; power supplys are usually the "it just shut off" or "it wont turn on" variety of death. They can do that though, if they start to go and the voltage gets irregular - causes all sorts of funky things.
HP + 8 yrs. old = ATX type mobo and power supply. I'm pretty sure a decent repair shop (check the yellow pages for a local joint) could fix it in about an hour or at least give you the lowdown quickly. If its the actual mainboard, fixing it would cost some significant coin - enough to take a look at upgrading to a new system. If you do go there, ask them to install your old HDrive in the new system as a slave.
Don't take it to "The Geek Squad". They will try to sell you a new eMachine and try to sell you on some "optimization" package. Be very afraid.
Hope this helps.